I thought it meant "our beer is everything (to us)" ...

I have no idea why I typed "Our beer is all". That doesn't even make sense.

Uh, "empty" is not in the hover list for beer...

Oh, losing a heart to a slang expression I couldn't have figured out on my own.

Nice didactic touch, duo...

Seems to be an idiom. "alle" does not seem to mean "empty" otherwise.

It is still not a good translation, it should be "gone".

This may be an idiom, and when one is just learning the language or a certain part of the language, throwing a curve ball like that, though will now stick, is really not as helpful as it may thought to have been. Why not create a section called idioms?

what other cases is it used for?

I guess it is at least for all type of drinks so in servings as in bottles/containers.

A more idiomatic translation would be "We're out of beer".

why empty??? empty means: leer

lol, It's same in Russian) The word "all" in slang means "the end". Actually it has an analogue in English: "That's all. We are going home". Hope this helps