Press on the Bottom and a membrane will break, activating a chemical source to heat it up

There is (was) also a cold version for the summer

Flavor wise, it's terrible

Now that I think about, I don't see this stuff on the shelves from decades ago. I wonder if they went out of business or if recent laws don't allow those chemicals on disposable items anymore

Edit: it's also disappointing, the first and last time I tried this product, I was initially excited as the container is just a little smaller than a coke can, but due to the double insulation to let you hold it without getting burned, the actual liquid content is like 10ml. And expensive, 3 euro which at the time was 4x a espresso coffee at a bar counter, properly prepared