The third option beyond MREs and HDRs (heh heh, I love the army's obsession with acronyms) are so called Heater Meals or Jimmy Deans. Heater meals contain a tub style TV dinner and a heater. "Jimmy Deans" contain off the shelf ready to eat canned food in single serving all inclusive meals (there is probably a correct name for them, but most people call them Jimmy Deans). Its what the Army feeds people when they don't feel they need an MRE. Like missed meals in garrison, versus giving you a field ration.

From one of the pictures I saw on Yahoo the "Jimmy Dean" is what I'd expect. The caption said MREs but the box definitely wasn't an MRE box, looks like the "Jimmy Dean" meal box. They're generally horrible, I'd much prefer an MRE. I think they may have the benefit of being cheaper then MREs. They'll have canned macaroni and cheese, canned frank and beans, Bumblebee Ham salad, etc. plus a few extras like canned fruit cocktail or Pringles. This is where a small stove will make its weight as several of these things are fairly nasty cold, but much better hot.