Pre-hydrate

When you drink a lot of water or other liquids in preparation for a night of heavy drinking in the hopes that you won't wake up with a desert in your mouth the next day.

aka 'prydrate'

Rodney: "Hey Herbert, you sure are drinking a lot of tea"

Herbert: "Yeah, I'm going to that Japanese whiskey bar Ichikura tonight, so I wanna pre-hydrate"