Words for drink
Words for drink are usually uncountable: Coffee is more expensive than tea.
But when we are ordering or offering drinks, we can say either a cup of coffee or a coffee.
Two coffees, please. (= two cups of coffee) Would you like a beer? (= a glass/bottle/can of beer)
Some nouns can be countable when we are talking about a particular kind or about different kinds.
Chianti is an Italian wine. (= a kind of Italian wine) The use of plastics has greatly increased. (=the use of different kinds of plastic)