Where can you get the infinite root beer?

Can you summon them anywhere you want? Can you summon them inside other people to kill them?

Can you only summon them right in front of you?

Is there just a place that when you take one, another one appears? If so, what would happen if you held your hand where it was supposed to appear?

For all 4 cases, what happens to the air where the cans appear?

Is there just a portal from where you can put your hand in to grsb the beer? Could you push people in the pirtal?