I tend to eat quite a lot of fruit. Oranges, bananas, and apples are the most common. I also take sandwiches for longer rides. I like cheese, butter, and some salad and veggies, though sometimes I will carry sliced tomatoes or something separately so as not to make the bread soggy.
I normally carry some powder mix for an energy drink, and a spare banana in case of the bonk. A half litre of energy drink + banana will usually get me to somewhere that I can rest and refuel.
Edited to add: when touring, breakfast really is the most important meal of the day. Don't skimp. Eat as much as you can hold & still ride comfortably. You'll burn it off, anyway.
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom