One time, I saw someone on Reddit say "if you're craving something but you don't know what, it's almost always water." I've always been pretty well hydrated, but I've followed that guidance since then and I can't think of a single time it failed me.
Hangovers are more often than not a result of lack of hydration. Start drinking water in between your pints at least. And also drink about a pint of water before bed. Hydration tablets with sodium in them too put in the water you keep with you overnight is a great idea too.