My favorite (and probably most dangerous) food for all day studying is ramen. Nothing like a big bowl of quick sodium to keep you going. It blends well with the sweat and tears that comes with doing problem sets all day. I hate studying. Much rather do a paper.
Honestly though– what is it about ramen that is so addictive? I'll need to detox after the study period is over. Detox and sleep: The two words that are getting me through this week.