The stations all seem loaded with chain fast-food places. It's for another thread, but maybe worthwhile discussing whether any of them are any good. They're the sort of place I tend to avoid, though that's becoming harder and harder.
KFC is all but guaranteed, followed closely by the Kungfu place, and McDs/BK. I also don't care for that stuff (and feel guilty about importing its odors into the air tight cars), but the food on kitchenless (e g. C, D, and G) trains really is amazingly bad. I suppose convenience store snacks may well be the lesser of all evils, apart from forgoing food altogether (possible on sub ~2.5 hour journeys, especially if you don't start out on an empty stomach).