a beer barrel的用法和样例：
- Two glasses of cider and a beer, please.
- For reasons best known to himself, he drinks tea from a beer glass.
- He plunked a dollar down at the bar and ordered a beer.
- Please tell Charles to replace the beer barrel; this is empty.
- In the evening we would drop into a roadside pub for a beer and sandwich.
- The draft you take from the beer barrel is enough for ten people.