I remember my first longest ride (15 miles, shop ride) I didn't eat beforehand and came home, made a four egg omelette with cheese, three pieces of toast, and a big iced coffee and downed it standing up. I then went over to the couch and fell into a deep sleep for the next 2 hours.

Now I eat beforehand. A piece of bread with a swab of peanut butter, folded over. Or a bowl of cereal (but warning: most people can't have milk in their stomachs on a ride - it doesn't bother me but it may you.) When I get in to work I have a banana or a pop tart and drink about 2 litres of water until I go home.