Coke. Not Diet, not Zero, not Cherry, not Vanilla, when I need it to really hit the spot it's plain Coke.
In college there was a time when I'd pound three to four cans of it a day. If it wasn't so bad for my teeth I'd still be doing it.
If you think that seems excessive, I used to work with a guy who'd drink two 24-oz bottles of Mountain Dew a day before he even got to work. He switched to diet after his doctor told him he was going to get diabetes if he kept it up.