I know that I will be drinking coffee if I stay up late, so to help with that I drink two cups of water for every one cup of coffee. I also try to drink a smoothie (check out my smoothie recipe) or an organic juice; just make sure the juice doesn't have a lot of sugar in it. I also skip the twizzlers and chips and have some braided pretzel twists, these seem to have less salt than other brands. Or I have an apple (which supposedly helps wake you up better than coffee) or carrots or some other healthy snack that's crunchy.
The basic rule here is to fill your body with nourishing things, rather than junkcso your body has fuel to work off of the next day. I also make sure to drink lots of water during class too. The action helps me stay awake, this way I don't slump and drift off in my chair. Plus the water helps me feel a little more refreshed so I can make it until nap time.