I often have peanut butter and banana sandwiches, albeit only on days when I'll be riding in to work1 - failing that, I generally go for a couple of pieces of fruit (usually a banana and an apple or orange) or make myself a smoothie or similar (a handy use for banananananas that are past their best). And tea/coffee, of course.
I do eat cereals, but a change is as good as a rest.
1 - I'm diabetic, so such things only feature in my diet if I'm actively exercising. Otherwise, YMMV.