Peanut butter on sliced apple, or banana. (PB and banana makes a good sandwich, too.)
You'll still be stuck with sandwiches a lot, I fear-so vary the bread. Tortillas, bagels,ect.
If you have access to a microwave, bring a big potato and bake it. maybe top with a slice of cheese, or anything, really.
A bag of tortilla chips or pita chips, and a jar of good salsa, or hummus, perhaps?
I like chopped apple mixed with vanilla yogurt and raisens and nuts. The apple will darken a bit, but that's all right.
Flavored yogurt instead of milk on cereal is good. Find a breakfast bar you like. Make a fried egg sandwich, add stuff like cheese and meat and mushrooms when you can.
Milkshakes, use a banana, other soft fruit, you can add peanut butter, chocolate syrup, canned fruit(Not all at once, obviously ). Throw in a scoop of protien powder if you like. And Milk, and or ice cubes. Doesn't take long to blend, you can take it with you to chug. Save a big plastic cup and lid from a fast food place. Washing the blender isn't hard. Put in a little water, close the lid, hit the button-that makes it faster.
My mother had an old fashioned shake blender that was a glass jar, a metal lid, and a metal plunger piece you pulled up and down quickly. We'd use milk, an egg, a spoon of sugar, and maybe a little vanilla. (This was before we knew not to eat raw eggs). It made a fast eggnog to chug, when time was short, and it was too early to face much food.
Make pasta salad to bring with you? That can be filling, and you can add a variety of stuff to it.
A can of tuna, or other meat, and crackers to spread it on. Not fancy, but no refridgeration needed.
Invest in a couple of cold packs and an insulated bag for lunches?
Eat anything fast and hearty in the am, not just traditional breakfast food. Leftover soup, chicken, pizza, ect.