I generally rely on coffee and camaraderie to keep me awake. Grab a cup of coffee and someone interesting to talk to, and you should be able to remain sentient. Doing something helps too--stay in motion, play a game which requires your attention... anything that requires active interaction to do is often a good way to stay awake.
Therefore, buy a cup of coffee, grab your friend/girlfriend/boyfriend/acquaintance/interesting stranger, and go for a walk. You should be able to stay awake, have a good drink, and get some good conversation in.
The most obvious way to stay awake through a whole day, though, is to sleep through the night. All-nighters, as fun/necessary as they can be, are generally to be avoided.