Find a solid surface on which can will be crushed. It should be strong enough to support the can and the large mass used. I have chosen the kitchen floor for my surface. It provides a nice solid yet slippery surface adding just a little to the difficulty factor. If you want to be safe, pick a surface that isn't so smooth.
I have chosen to apply 185 pounds of force on my can to crush it. A cylinder will support a large amount of force if applied properly and directly. After I have place the mass on top of the can, a slight adjustment to the positioning of the mass causes the cylinder to fail. Once that happens, a cascade of failures causes the can to be crushed flat. (see video)