Abstract: A disposable heating unit for use for heating the contents of a container, includes a first region containing a combination of at least two solid substances which undergo an exothermic chemical reaction which is not spontaneous at room temperature. Adjacent to the first region is a second region containing at least a first reagent. A storage cell is configured for releasing the liquid containing a second reagent into the second region. The first and second reagents undergo a spontaneous exothermic chemical reaction when brought into contact, thereby initiating the exothermic chemical reaction of the solid substances.