My son is not generally a fan of cold meals or sandwiches. I bought a funtainer food thermos for my son last year. I would fill it up with hot water when I made breakfast in the morning (I use my kerig). I'd let it sit while we got around. About 5 or 10 minutes before walking out the door, I'd nuke lunch. Dump the water (dry it with a towel so food doesn't get soggy) and fill it with the food. We tested it. It works really well for about 4.5 - 5 hours. My son never complained about lunch not being warm. We used that thing to bring everything under the sun to school...chicken nuggest, dinner leftovers, fried rice, steamed veggies,cous cous, hot dogs (covered with hot water and assembled at school), cheese dip, soups. We even cut up pizza a few times and sliders fit in the container too. It works to keep things cold as well, my son liked when I put his fruit salad in there.