Crushing Can Demo - Mega Can
Please don't try this at home.
Crushing can demo can be done with a simple soda can, but of course we needed to do it on a larger scale. It is done by heating a little water in the can until it boils. Normally you dip into cold water, but on the larger scale we had to add ice, causing a delayed crushing reaction.
What's happening? When you heat the water it creates water vapor. Cooling the can causes the water vapor to suddenly condense back to water creating a partial vacuum. The low pressure inside the can and high pressure outside the can, caused it to collapse.