Anything with too much sugar/carbs will make you sleepy... cereal, high-carb bread, pancakes, etc., are all sleep inducing -- unless you combine them with a protein source (eggs, bacon, salmon, tuna, beans, etc.)
Processed food is generally worse for you than something natural... Pop-tart << fruit cup < actual fruit.
Pick the protein source first, then add some carbs (fruit, yogurt, toast, quick oats, whatever) and make sure it has some fiber in it.