These are important questions that will be asked by your players if they haven't gone there already. DMs, pay attention. Have a solid argument planned out beforehand or suffer the consequences. The thirsty, withered consequences.

Personally, I argue that Create/Destroy Water can't target a creature therefore get fucked, cast it somewhere else or pick a different spell. Why that is, scientifically? No idea. Same reason you can't Revivify a kitchen table. Logic dictates that you could turn it back into a tree, in practice nothing happens. It's A Secret To Everyone™