Originally Posted by
rsvman
I don't know how to tell you this, but your friend was at least partially right.
The reason soda spills out when you open the can or bottle is that carbonation that is close to but below the surface escapes when you open it, and it takes some of the liquid with it.
If you tap gently on the SIDE of the can or bottle, this allows said carbonation to escape into the air above the soda, so that when you open it, it can escape without bringing the soda along.
Most people tap the top of the can, as if they are going to push the carbonation down into the soda. That doesn't work. But the tapping the side of the can actually does. If you do it with a bottle you can actually see it work.