Apparently the self-heating is chemical, triggering whatever mechanism mixes a quantity of quicklime with water, and the result is exothermic.
I tried a self-heating coffee once and to be fair it did heat up pretty well, but the coffee was overly bitter and kind of gross. With the right coffee I could see this being quite nice.
I remember in Japan they had both! Pretty cool.
I only ever had the cold variety in Japan, but I can imagine the warm variety being nice as well.
These are aluminum cans, I presume? Is the “hot” coffee more like lukewarm coffee or is this something that one would only be consumed in the winter when one is wearing gloves?
Yes, nowadays all cans are aluminum though they used to be made of steel. The hot drinks are hot hot, not lukewarm hot.