Is "coffee" a countable noun?
It can be countable and uncountable.
It depends on the context.
when it's uncountable the meaning: a drink made with ground, roasted seeds.
Example sentence: How much coffee do you drink every day?
when it's countable the meaning: one cup of coffee.
Example sentence: How many coffees did we order altogether?"
It depends on the kind of sentence. It can be both countable and uncountable