Not quite in college yet (believe me, not for lack of wanting... total senioritis case), but in my experience it depends on the teacher. One teacher I had actually got us all to get up, turn the lights off, and turn the clock ahead six hours when a girl fell asleep for the upteenth time, so that she'd be really disoriented when she woke up. We were on our way to conduct class from an empty room nearby when she woke up and ruined our fun... it was almost tragic. Personally, I try not to fall asleep in class very much, though the last time it happened I did wake up about ten minutes before the end of class. Then I remembered how much of a joke the class was, put on a lullaby and went back to sleep.
As for eating, most teachers know how disgusting the school food is, and that it takes us our whole lunch break to go out and get good food sometimes. Mostly they're flexible about such things. Mostly these days, they're more concerned with cell phones and mp3 players than sleeping and eating.