Instant temperature changing device includes reactant and activator liquid that generate an exothermic or endothermic chemical reaction when combined to heat or cool contents in the device. One temperature changing device includes an inner shell and an outer shell, an activator container, and a reaction chamber. Opening the activator container causes reactant to combine with activator liquid and undergo an exothermic or endothermic reaction to initiate heat transfer to or from the contents disposed in the inner shell.