I was in my worst flare during my last semester and I also talked to my professors and they were very understanding after that and didn't take off attendance points if I had to leave class early some nights. I didn't live on campus, so I didn't have to eat campus food, but there should be some choices on campus that aren't as bad as others. Even Wendy's carries grilled chicken sandwiches that don't bother me. It's just a matter of making good choices when faced with bad ones as well and learning what does and doesn't bother him. I also think he should keep a food diary.
As far as drinks go, the only thing I drink other than water is diet caffeine free stuff. Not real tasty, but keeps my stomach from getting upset by the caffeine. As easy as it is to keep handy, quick snacks around, limit those with a lot of sugar or fat. Baked chips work for me, but I know some of them can cause problems for some people if they have olean or other stuff like that in them. Carbs really seem to help settle my stomach, so I'm big into crackers (goldfish, saltine, kinds with cheese in between them, etc.) for easy snacks. It may be embarassing or hard for him to not get to eat what all of his friends are eating and to seem like a "picky eater," but it's better than the alternative. It's just something he has to decide to do. My boss's daughter was recently diagnosed and she is in college and just isn't willing to forgo the "normal" college food yet.