I don't even get up to pee in the middle of the night, much less get up to drink anything. I can't be arsed. (And yes, I have an excellent bladder before anyone asks, I can hold it forever - even while asleep.)
My ex was a little bit like this.. He never slept more than four hours at a time on average, and he was never tired that I could tell. Kinda drove me crazy. (Among other things..)