How do you work hello kitty hand warmers?

Hello Kitty hand warmers typically work by utilizing a chemical reaction to produce heat. They often contain a supersaturated solution of sodium acetate; when you bend the metal disc inside, it initiates crystallization, releasing heat. To reuse them, you can boil the hand warmers in water until the crystals dissolve back into a liquid state. Once cooled, they're ready to provide warmth again.