I'm wondering whether a character could spread holy water over his sword or axe and then hit an undead and on the first hit, inflict an extra 2d6 as if the holy water had been thrown at the undead. After all, we can do that with poison and holy water is like poison to undead creatures.
- Anybody can ask a question
- Anybody can answer
- The best answers are voted up and rise to the top
By the book? No.
As a house rule?
Consistency may be a problem. Poison for applying on blades is usually described as a paste or oil - something that can stick for a while, as opposed to an ingested poison which would be watery.
The holy water itself wouldn't stay on the blade long enough to hit something with. It may be able to (temporarily) make the weapon holy, but this would be entirely up to the DM, and not covered by the rulebooks.
RAW, you need to make a ranged attack with the holy water, as an improvised weapon.
It's right there on PHB151
Should you houserule it, I would suggest that allowing the full effect of the holy water in addition to the effect of the underlying weapon breaks the action economy. Also, possibly the holy water economy.