I just got this from a member of a Tennessee fly fishing board.
He likes hot Burritos for lunch which he prepares the night before wraps in aluminum foil and stick in the fridge. In the morning he preheats the oven to 350 has coffee and pops the Burritos in the oven along with a brick wraped in 3 layers of aluminum foil, the Burritions on the center rack the brick on the bottom. By the time he has showered and dressed everything is nice and hot so he puts a towel in the bottom of a lunchbox size cooler, places the brick on the towel, layers his Burritos over the brick and covers them with another towel. He claims that the Burritos will still be toasty warm at lunch time.

I will be testing this "Hot Lunch" method on my next trip to the Elk River. There is gas station/general store on the way that has a nice selection of hot sandwichs and great Broasted chicken. Fish below the dam, have a hot (I hope) lunch and then head down stream for the afternoon.