For example, a Bard with a bag of holding, grabs a vial of acid from his bag, and throws it at the goblin.
My assumption is, this would take two turns?
1st turn, "Use an Object", grab vial.
2nd turn, "Improvised Weapon", throw vial.
Or is it just one turn? A DM had mentioned that the "Use an Object" feature is only if it's something relatively difficult, like: Pulling a rusted floor switch. And that grabbing a vial from your bag is a free action.
I had to look it up to confirm, but you are correct. It would take two rounds, to retrieve an item from a bag of holding and subsequently attack with it.
I had thought it might be a bonus or move action (like drawing a weapon), but the item description is clear:
Retrieving an item from the bag requires an action.
Don't forget that the bag of holding does not state that you automatically greb the item you are looking for (opposed to what a Heward's haversack does). So if you have a large pile of junk in your bag of holding, grabbing your shield is likely an action, but trying to fetch the single potion of healing amongst the 3000 coins, items and junk in it is as difficult as if the whole content would be strewn on the floor or on the table. So I guess this is DM territory to determine how long it takes to retrieve this. Personally I don'r make a difference whther this is strewn on the floore, in achest ort in a bag of holding, I call for Perception checks with DC according to the difficulty to retrieve the item and upon success the item is grabbed, else you need to go on looking for it.
THis will better answer your question : Handy Haversack vs. Bag of Holding
PHB 190, Other activity on your turn:
You can also interact with one object or feature of the environment for free, during either your move or your action. For example you could open a door during your move as you stride towards a foe, or you could draw your weapon as part of the same action you use to attack.
PHP 193, Use an Object (as an action)
You normally interact with an object while doing something else, such as when you draw a sword as part of an attack. When an object requires your action for its use, you take the Use and Object action. This action is also useful when you want to interact with more than one object on your turn.
Using the above two references drawing a vial from a belt pouch would be a free action. Drawing a object from a backpack would be a Full action. In either case throwing/drinking/deploying ext also takes an use object action.
I don't have the text for the bag of holding I believe the activation is you place your hand in the back of holding and mentally call the item you want retrieved. If the bag of holding is a satchel placing your hand into it can, call an items name and withdrawing it could be interpreted as a free action as part of a move.
In contrast you could focus on using a magic item (bag of holding) is an action. I believe that this can be interpreted by the DM on if the bag of holding behaves like a belt pouch or satchel or a magic item.
Depending on this interpretation is could be: one free action (dependent on you having a free hand) and one action; or two actions.
