I usually stop playing and take a break to eat. If I've been playing for a little bit and I'm lightly hungry - Chips. If I've been playing for a while and I got the munchies - Those awesome spicy bowl noodle things that you add hot water to. If I'm on a couple hour marathon - Gigantic sandwich with anything I can find on it.
If I'm pulling an all nighter and I'm in need of immediate sustenance... S*** gets ugly and I have all three with a Dr Pepper.