For protein, you can include a 3 oz can of tuna (leave sealed until time to eat), chunked chicken
or turkey, cheese, etc. You can do the same thing with healthy
sandwich fixings - sliced turkey, chicken, left over roast beef on whole grain bread or wraps. Pack Greek yogurt, raw veggies, fresh fruit, homemade soups that you can heat in the microwave. Any healthy leftovers that can be put in containers and microwaved.
The important thing is to be sure to take them with you.