The so-called smart cans created in South Korea are a very interesting type of application of physicochemical heat exchange phenomena.
These cans get hot or cool. Smart cans used for soda and beer freeze the product in 15 seconds without the need for a refrigerator.
Inside the can is a coil full of carbon dioxide under high pressure. When you open the can, the gas is released, causing a rapid cooling that freezes the drink contained in the can.
There are also containers that heat their contents. It is used in soups, milk and coffee.
This idea was widely used during World War II to provide hot food to soldiers on the battlefield.
For heating, various heat-releasing (exothermic) reactions are used, such as:
CaO + H2O → Ca (OH)2
2 Al + Fe2O3 → Al2O3 + 2 Fe