Heater bag with 10 heat bags and 10 zipper bags (for own food)
The heater bag works just as well as the lunch box. The advantage of the bag is that you can heat several meals in the same heat bag.
You can also boil / heat coffee / tea / gruel with a metal bottle or glass bottle. However, no thermos.
The zipper bag is for bringing your own food. You can store food in the fridge / freezer before you go on an excursion!
The zipper bag can be washed and used several times.