"Vaper's Tongue" is really the same thing, in most cases, as "olfactory fatigue" -- you grow so accustomed to a certain smell, you no longer smell it? (like the scent of your own home) Applied to taste. Best way to avoid or fix it is to have several (or more) different flavors available and ready to vape at all times, and it's good if they're different "profiles" -- like, a fruit, a
tobacco, a pastry, etc.
Tons of water is not necessary unless you're also exercising a lot, or sweating abundantly for any other reason -- as some of us middle-aged ladies can attest

. But there is such a thing as "water intoxication" from excessive water drinking, and it can kill you. Any liquids that don't contain caffeine, alcohol, or *excessive* sugar work just as well, and that includes foods that contain a lot of liquid - fruit, soup, etc.
Andria