I tried making an air tight lid to save sodas for later. This is as close as I could get. It fits very tightly depending on the brand.

On some cans I could fill with water and turn them upside down with no leaks but if I squeezed the can it would leak so it's a tight but not perfect seal.

I also noticed that this varied from brand to brand. On Pepsi it fit the best. Very tight (takes a bit of force to put on). Brisk tea was a bit loose, still stayed on but not water tight. Diet Rite it fit good but not as tight as Pepsi...