beer与beers
1. 表示“啤酒”，作为物质名词，不可数；表示种类时，可数。如：
Some people don’t like beer. 有些人不喜欢喝啤酒。
Beer has a very distinctive smell. 啤酒有特别的气味。
There the beer was specially good. 那里的啤酒特别好。
They buy less beer and fewer cigarettes now. 现在他们买的啤酒和香烟比过去少了。
Most beers are made from barley. 大多数啤酒是大麦酿制的。
2. 在口语中，可表示“一杯(瓶、罐)啤酒”，此时是可数名词。如：
Two beers, please. 请来两杯啤酒。
Help yourself to a beer. 喝杯啤酒。
Would you like a (glass of) bear? 喝杯啤酒吗?
Two beers, please. 请给我两杯啤酒(from www.yywords.com)。
There are a few beers left in the fridge. 冰箱里还剩几罐啤酒。
We went to a bar after work and had a couple of beers. 我们下班后到酒吧间去喝一两杯啤酒。