Friend with Ulcerative Colitis Keeps Getting Flare-ups When Visiting

Everytime (twice) my friend comes to visit (he lives 2.5 hours away). He gets a horrible ulcerative colitis flare-up and has to drive home. Last time he was in the hospital for a week. 😥 He doesn't know what triggered it. I suppose it could be stress as he doesn't like leaving his house very much, but he is pretty comfortable with me. He just drove home about 4:30 am. He was feeling a little sick before he came over so at least I know it's not completely triggered by this environment. Those with UC, what are your flare-up triggers? I will also say it feels like he hardly eats, which I would feel could not be good, having an empty stomach. And he pretty much only drinks Gatorade. As someone who always drinks lots of water all day, I don't know how people survive without drinking water. Any personal insight appreciated. Thanks.