I am just going to jot down things I remember putting in DD lunch box also things I still use for my own today.
Breadsticks - the hard crunchy ones
Rolled, deli meat and cheese
Ritz cracker sandwiches - Use Ritz cracker or whatever you have, add in items like deli meat and cheese, peanut butter and jelly, Bacon, lettuce & tomato, mozzarella and plum tomatoes.
Ranch dip and raw veggies, make sure they are cut up small.
Grapes, strawberries, plums, apples, if you send cherries make sure to pit.
Fruit cups in juice, boxes of raisins, fruit gummies snacks, granola or cereal bars.
Pickles
Ramen noodles in a thermos, DD loved them, I would heat up to boiling and put in a thermos ( I did get a really nice one that would hold the heat and not leak) and they would be to temperature by lunch time.
Chicken noodle soup and crackers.
Gold fish crackers.
simple homemade pasta salad - not mayo style.
Lettuce wraps - filled with everything you can think of, chicken salad, turkey salad, deli meat and cheese,
Chips, crackers, pretzels,
100 juice boxes, or bottled water w/ flavoring package - you can freeze and they should thaw by lunch time.
That's all I can think of right now.