I did a loaded tour with a strict vegan friend. It was at times a real pain to find food for him, sometimes at a restaurant he would just order dry baked potatos. He had no trouble on the bike, though, when we were doing 80-100 miles a day for 6 weeks.
I, on the other hand, will eat anything on a ride, or any other time, without thinking much about it. I do enjoy my rides, and I have found the more I ride, the more I can eat while riding, up to 6000 calories a day while touring with a total load of 270 pounds.