Why doesn't a soda-pop can "overfizz" after it falls inside the dispensing machine?

Pssst… looky here. And here.

And most importantly, here.

Next week, we’ll examine what tapping does to ciggies…

Have you ever used a Pop-Shop carbonation device/
Or This Soda Stream carbonation device?

C0-2 is forced into solution like nitrogen to a diver using SCUBA.
When we pull the tab on a soda can its like a diver surfacing from deep and the gas that is held in solution is freed and we see it in the bubbles because of the surface tension of the liquid.

Now shake up a can of soda and hand it to your buddy and unsuspecting he opens it and a jolly mess is seen.
Now with a Cold can, shake it up real good then put a good hard squeeze to it for 10-15 seconds then release the squeeze “Slowly” and pop it open. Done correctly(Gas forced back into solution) it will be back in the same state of fizz as before the shaking.

I remember in some of the non refrigerated machines (although they died out in the 70s lots of backcountry no electricity places still had then ) they did go over occasionally …which is why older people would wait to open a soda from a machine

When I was a kid we used to like to spritz each other with a freshly opened can o pop. I recall root beer provided the best distance and volume of ordnance. These days, it doesn’t seem to be as dramatically different from other beverages. Am I imagining that, or is corn syrup killing soda pop as well?

I think Diet Coke (and the ilk) release carbonation more readily than sugar/HFCS-sweetened soda. It’s why the Mentos demonstration uses Diet Coke.