The heaters in the MREs that I bought were a sealed plastic bag that you tear open at the top. Inside is a pouch of magnesium powder (similar to chemical handwarmer pouches, if you are familiar with those.) Included also is a packet of saltwater (similar to a ketchup or mustard packet, but larger. You open the saltwater packet and pour it into the plastic bag onto the magnesium power pouch. You then slip the MRE serving into the plastic bag and fold the top of the bag over, then slip the plastic bag into a flattened cardboard sleeve and lean it against a rock or something for around 10 minutes. A lot of the heating ability–I assume, comes from heat being held in by the cardboard sleeve. But the sleeve could fit an unopened can of soup which you could heat then open afterwards. I see no reason that it shouldn’t work.
Actually, those are likely left over government purchased food boxes. I happened across a listing not log ago on a government suction site for something like 5,000 - 10,000 pallets of those boxes that were nearing expiration. I remember it because I was so intrigued that I did some math to figure out how many 50’ semi-trailers those pallets would fill - it was in the hundreds. Someone with a huge logistics capability likely got these for pennies per box (or less, maybe even boxes per penny) and sold them to those type stores all over the country. Heck, even if the buyer only made $0.10 per box after shipping cost, they would still have netted big bucks.
Interesting. Here is a closed suction for 232 pallets of 800 meals per pallet (185,600 meals) that sold for $52,095, or 28 cents per meal. These aren’t the kits I’ve been describing, but the small white boxes (the 5th photo when you mouse-over) look very much like a small box that one of the surplus stores near me sells for $1.00.
And here is one for 28,607,904 meals (similar to the above but not to mine) that sold for $405,656, or 1.4 cents each. (Description says 26 pallets per truck, so that’s 1,134 trucks for that one lot.)
Those kits are what they give people here for food assistance.
That is the one I saw. I lowered my estimate of pallets because I thought I had to be remembering the quantity wrong. The sheer quantity boggles the mind.
More googling yesterday turned up another set of auctions for people on a tight budget who were buying only a single truckload at a time, or 20,000 to 25,000 meals. The lowest winning bid for one of those was $350, which matches the 1.4 cents per meal (at the 25,000 upper end.) Never did find a “smoking gun” for the exact type of boxed kits I’ve been finding, though.