To keep lunch warm when packed wrap the lunch in aluminum foil and use an insulated lunchbox or insulated lunch bag.
You may also consider using a warming lunch bag that plugs into a 12 volt outlet in your vehicle.
If you have warm lunch in a container wrap the container in aluminum foil as well to help hold the heat in.
Pack hot or grilled sandwiches inside aluminum foil to keep them warm, or if you have access to an oven come lunch/snack time, you can toss it directly in the oven to warm it back up.
For cold sandwiches, try wrapping then in parchment paper, which can also act as a place mat when you unfold it.
The easiest and most common method for keeping food hot while traveling is wrapping up the food in aluminum foil and towels.
This will help to keep your food hot for a few hours or if you're traveling with a large quantity of dense food (eg. a soup or casserole) it can stay hot even longer.
Bento Boxes do keep food warm for at least a few hours.
If you place the Bento Box with warm food in an insulated bag then the food will stay warm for around 4 hours.
A bento is a single-portion take-out or home-packed meal of Japanese origin.
Outside Japan, it is common in other East Asian culinary styles, including Chinese and Korean cuisines, as rice is a staple food in East Asian cuisine
The great thing about bento boxes is that you can build any kind of meal you need thanks to the compartments.
The best option is to use it to fulfill your daily food groups, even packing it the night before, because compartments will prevent things from getting soggy.
The word bento is originated from the Japanese language which means lunch box.
During the fifth century, Japanese man used to carry compact meals so called Bento when going fishing and hunting.
Through that period Bento boxes contained white rice, millets and potatoes.
Bento boxes have grown in popularity, not just because of the nutritional value of the meals, but also because they're also aesthetically pleasing.
Often foods are arranged in the bento to look like popular characters like Snoopy, the minions and, as in this case, the Simpsons.