Are there any official rules for what happens when a character goes without sleeping for a day or more?
Ravenloft Dungeon Master's Guide p. 30 states:
Sometimes a hero may need to carry on in the face of his worsening physical and mental exhaustion. After a full night’s rest, a character can remain active for 16 hours (20 hours for elves) before tiring. At the end of that period, he must succeed at a Fortitude save (DC 15) or become fatigued. If the character decides to stay awake, he must make another Fortitude save every four hours. Each successive saving throw increases the DC by a cumulative +2. For example, a human resisting sleep makes Fortitude saves at DC 15 after 16 hours, DC 17 after 20 hours, DC 19 after 24 hours, DC 31 after 48 hours and so forth. The Endurance feat grants its +4 bonus on these saving throws.
A fatigued character who fails a second Fortitude save to stay awake becomes exhausted. Each time an exhausted character fails further Fortitude saves to stay awake, he suffers a cumulative -1 penalty on all attack rolls, ability checks, skill checks and saving throws for each failed saving throw.
In addition, whenever an exhausted character experiences a calm, quiet moment of rest, he must succeed at a Constitution check (the character adds his character level to this check) to avoid falling asleep. The DC of this check is 10+2 for each Fortitude save the character has made to stay awake.
All penalties for lack of sleep return to normal after a full night of complete rest.
But is it official? Yes. The book states:
Ravenloft, D&D, Dungeons & Dragons and its logo, the d20 System logo, and Wizards of the Coast and its logo are trademarks of Wizards of the Coast Inc., a subsidiary of Hasbro Inc., in the USA and other countries, and are used by Arthaus under license.
It also bears WoTC's seal for a official licensed product.
Now, it is third party. While having nothing to do with its official status, some tables will look down on it because of that (usually with very poor reasoning). Some admit its status, but limit it to the Ravenloft Campaign Setting. To which the book states
Although Ravenloft is a freestanding campaign world, nothing says you have to use it that way. This section examines several ways for you to use Ravenloft's horrors in your game. (p 22)
Nothing especially important in core is required to happen (you don't heal or recover spells), but there are optional rules to stay up with consequences.
You no longer are healing in core.
With a full night’s rest (8 hours of sleep or more), you recover 1 hit point per character level. Any significant interruption during your rest prevents you from healing that night.
If you undergo complete bed rest for an entire day and night, you recover twice your character level in hit points.
You can no longer recover spells in core.
To prepare her daily spells, a wizard must first sleep for 8 hours. The wizard does not have to slumber for every minute of the time, but she must refrain from movement, combat, spellcasting, skill use, conversation, or any other fairly demanding physical or mental task during the rest period. If her rest is interrupted, each interruption adds 1 hour to the total amount of time she has to rest in order to clear her mind, and she must have at least 1 hour of uninterrupted rest immediately prior to preparing her spells. If the character does not need to sleep for some reason, she still must have 8 hours of restful calm before preparing any spells.
There is an optional house rule for not sleeping.
The game has no rules for trying to stay awake through the night, writing down every word someone says without a mistake, or opening the stuck lid of a container without spilling a single drop of its contents. However, in the course of an adventure any of these situations could potentially make or break an encounter. You have to be ready to make up checks for such non-standard activities.
Using the example situations above, staying awake might be a Constitution check (DC 12, +4 for every previous night without sleep), with an elf character gaining a +2 bonus on her check because an elf is only giving up 4 hours of trance instead of 8 hours of sleep. (DMG 33)
So, by core, and if your DM doesn't care, you never need to sleep unless you need to recover spells or heal, but they may make optional rules or house rule it.
There's nothing official about what happens if a creature that must sleep fails to sleep beyond some creatures being unable to regain the the use of some of their abilities. However, a DM can extrapolate house rules from existing material. For example, the Effect of the flaw Insomniac (Dragon #328 43–4) says
In order to get a full night of rest you must succeed at a DC 15 Fortitude save. If you are sleeping and a disturbance wakes you during the night, you must make an additional save (at the same DC) to return to sleep. If you fail the Fortitude save you are fatigued when you rise in the morning. If you are fatigued when you try to sleep, you gain a +2 bonus on your save. If you are exhausted, you gain a +6 bonus. Comfortable conditions, such as those found in most inns, grant you a +4 bonus on this save. Poor conditions, such as sleeping on the ground or in armor, give you a −4 penalty on this save. Even if you sleep poorly, you may prepare arcane spells as normal after 8 hours of fitful rest.
A house rule based on this could go something like this:
You normally automatically get a full night of rest. If you are sleeping and a disturbance wakes you during the night, you may automatically return to sleep. If you do not get a full night's rest, you are fatigued in the morning. If you are already fatigued in the morning, you become instead exhausted.
However, the condition fatigued is removed by, for example, the 2nd-level Clr spell lesser restoration [conj] (Player's Handbook 272), so a house rule like this will make sleep a trivially-overcome burden for even lower-mid-level characters.
Another example on which house rules can be based is the Sign of the Apocalypse Appalling Fecundity when that sign is strong:
Living creatures that require sleep lose the ability to do so, as their bodies fidget and their thoughts race. Physical exhaustion sets in, and eventually minds break. A living creature can go without sleep for a number of days equal to its Constitution modifier (minimum one). Thereafter it is fatigued, remaining in this state for a number of days equal to its Constitution modifier (again, minimum one); if it would become fatigued during that time, it is exhausted instead. Each day after that period, the creature takes 1 point of Wisdom damage. If the total Wisdom damage exceeds its Hit Dice, the creature is affected as if by an insanity spell. Once its Wisdom score drops to 0, the creature becomes unconscious but cannot recover lost Wisdom naturally. Only a sleep or deep slumber spell or equivalent effect can grant rest for a time, after which the effects of the sign begin anew. (Elder Evils 9)
The emphasized portion of this description forms the spine of the house rules I've used successfully and without complaint from players for years:
- A creature that must normally sleep that doesn't sleep for its Constitution modifier in days (min. 1) gains the condition fatigued; it gains the condition exhausted if it would gain again the condition fatigued.
- A creature that must sleep that doesn't sleep for its Constitution modifier in additional days (min. 1) gains the condition exhausted.
- Each day after the previous span without sleep, the creature is dealt 1 point of Wisdom ability damage. If its Wisdom ability damage exceeds its Hit Dice, it is as if the creature were affected by an effect like the spell insanity (PH 244) except that the effect is extraordinary, there's no saving throw, and it isn't mind-affecting. If its Wisdom score is reduced to 0 by this Wisdom damage, the creature is unconscious. This counts as sleep.
- Only sleep or unconsciousness heals the ability damage and removes conditions caused by lack of sleep unless an effect specifically says it mimics or substitutes for sleep like the 4th-level Clr spell remove fatigue [trans] (Book of Exalted Deeds 105).
I think in a campaign a few years ago one PC went all the way to taking 1 point of Wisdom damage before finally crashing out, but I've never seen a PC willing to commit to madness to avoid sleep, nor have I as a DM put PCs in a position where they were driven mad because they were forcibly deprived of sleep, so I can't speak to these house rules' efficacy when taken to the extreme. However, unlike the more pedestrian Insomniac-flaw-based house rules above, These rules make it so a PC can go a few days without sleeping, but then the PC pretty much must sleep, and that's always seemed adventurer-like-enough behavior to my players.