Cool video.
Okay physics majors, how does this actually work, and what does the refrigerator magnet have to do with it? Does it matter if the beer is cold or not?
It doesn’t.
I think it’s a magic trick.
“Abracadabra”.
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Magnets in general have short ranges, and this is especially true for the high-multipole magnets you find in those little flat fridge magnets. There’s no way the magnet at the bottom of the bottle could have any detectable effect whatsoever on anything at the top.
I don’t need to be a physics major to know this is a trick.
how does this actually work
It doesn’t. Faking stuff like this seems to be a hobby for some folks.
what does the refrigerator magnet have to do with it?
It makes you think that there is something you don’t understand going on.
Does it matter if the beer is cold or not?
I seriously doubt that there’s even beer in the bottle. It’s probably a couple of reactive chemicals (could even be something like diet coke and mentos). By tapping and slightly shaking the bottle, it causes the chemicals to react and produce gas which pops the top. The bottle cap is most likely just barely held into place and can be easily popped.
Or, it could be someone’s digital video editing project for animation school. The bottle cap may not even exist in real life. Many of these projects are graded on how many youtube hits and facebook likes they receive.
Your premise - that it works - is flawed. It’s a well-concealed string pulling the cap off, a little sound editing to provide the anemic “fssst” of a bottle being opened, and a little video magic to provide the puff of condensation. You can even see the cap come off in two distinct movements.