What you eat before a ride kind of depends.
I know that I don't do well with greasy, heavy foods before a ride. I usually have a cup of coffee, a cup of milk, 2 hard boiled eggs, and a packet of instant oatmeal.
Since my commutes are relatively short (within 5 miles or so), I don't need to eat anything else for a little while. I don't think i have ever eaten on a ride, but I will bring along 2 PB&J sandwiches, an apple, and 2 hard boiled eggs for when I get hungry.