I have run into a conundrum.
When I go to get some friends cans of beer I say:
You guys want a beer?
When I am referring to going to a bar and drinking some I say:
Let's go get some beers!
When I go to a store to buy beer I say:
I am going to get beer.
How can I work this out? My friend is a native Chinese speaker and this is the sort of plural thing that trips her up. How is this explained?

