There is not a lot of variety when it comes to food on campus since all of the students eat in the places surrounding it. The American University of Paris is woven into the city, so it's not as uncommon as most people think it is to grab a French pastry for breakfast and pop into a café for lunch. Since there is no meal plan at the University, it is up to the students to decide what, when, and where they eat. It takes a while to get used to the absence of huge, student eating areas, but it is made up for with the abundance of surrounding restaurants.
The campus does, however, offer some reprieve for the hungry students who skipped breakfast because they were late for their morning classes: the Amex in the Bosquet building. Along with drinks like coffee and hot chocolate, the Amex offers a selection of sandwiches as well as some meals throughout the day (which don't kill a student budget). There is a Subway located in the Grenelle building (where most classes are held) which is also pretty good if you're in a hurry or just lazy. There are also some vending machines on campus which distribute sodas, water, and, of course, snacks.