Ask someone "What is your favourite comfort lunch food?" and a lot of people will be replying with tomato soup and grilled cheese sandwiches. When I was a kid, I was a walker. Meaning I was home every day for lunch and this combo was possible for me. It still is possible even if you pack your child a lunch to take to school.
My son is not big on sandwiches but he LOVES grilled cheese. So I figured I would try to see if it held up in a lunch box. So first thing in the morning I put on a pot of tomato soup and primed his thermos with boiling water. I threw together a grilled cheese sandwich. While I was standing there, it had occured to me that it may get soggy in the lunchbox if I put it in warm. So I just cooled it off on my baking rack before packing it away into his Goodbyn. Apparently it was perfectly fine when it was time for lunch! It was room temperature and perfect to go with his hot soup.
In this Goodbyn lunch is a grilled cheese sandwich, cucumber slices, baby carrots, dill pickles, jello cup, Babybel cheese, granola bar, brownie and a thermos of tomato soup.