Dust of dryness is the go-to object for removing water

The dust of dryness (Dungeon Master's Guide 255) (850 gp; 0 lbs.) affects water and only water (although the description listing several kinds of water). It gathers up to 100 gallons of water and turns it into a bead. If you throw the bead later it breaks and all that water reforms in that spot.

It has famously been used against creatures vulnerable to holy water… breaking the bead and deluging undead with 100 gallons of holy water yields an absurd amount of damage, the ramifications of which are beyond this question's scope.

As the dust is specifically called out to only affect water, it leaves all else untouched, which should result in your bead sitting in a pile of now de-watered ashes. Any irony is a bonus.