I do not use the lunch box, so I do not have ideas, but I think that it is preferable to put foods that do not change their taste with the passage of time
I like things that require very little preparation and can be quickly eaten during lunch. Sandwiches are a good one but I also know I should have fruits and vegetables and other healthier things.
Yes! My favorite lunch on the go is to get a flour tortilla (depending on the type of tortilla you may need to heat it up before starting). Then, spread some topping such as cream cheese, turkey ham, spinach, avocado, jalapeños, bacon bits, etc. (These are just my faves.) then you roll it up like a sushi roll and cut it like a sushi. Super yummy!
I'm a vegetarian so my lunch usually includes cooked vegetables, bread, a can of flavored milk and salad. And sometimes pickle and a local snack on the side