Great question! After doing some research, I have some evidence for you: here's a video that supports the idea that tapping the sides of a soda can minimizes explosions . (But note that this video is not a real science experiment, because they did not use a control group. They should have tested what happens if you shake a soda can and open it without tapping. After all, not all types of soda cans are the same--maybe none of the ones they tested could explode anyways!)

As they mention in the video, scientists think that the explosions are caused by bubbles of carbon dioxide gas. Where do these bubbles come from and what do they do?

Soda cans are sealed using special machines. These machines pump carbon dioxide into the can, then trap it under the lid. This gives the inside of the can a high pressure. Normally, most of the carbon dioxide sits on top of the liquid. But if you shake the can, some of the carbon dioxide gets trapped in bubbles instead. Most of these bubbles stick to the inside wall of the can.

When the can is opened, the pressure inside will be released, causing the bubbles to rise and expand. As the bubbles rise, they carry some of the soda up and out of the can.

Before you open the can, if you tap on the sides, you can knock the bubbles off the walls. The idea is to put all of the carbon dioxide back above the liquid. Then when you open the can, the pressure can escape without disturbing the liquid below!

By the way, it seems that this strategy works better on some types of soda than on others. It's possible that the bubbles in some types of soda are harder to dislodge than others. Some types of soda may have chemicals in them that increase bubble formation. But I haven't tested this theory, so I can't say for sure.