In English we can use phrases like "a beer" or "a coffee" (ref). For example, in the English dictionary, it says "coffee" can be defined as "a cup of coffee" which then becomes countable.

coffee [mass noun]

1 a hot drink made from the roasted and ground seeds (coffee beans) of a tropical shrub

• [count noun] a cup of coffee: she'll buy you a coffee.

• ...

In Spanish, I have also seen usages like "un café" and "un té".

• Are nouns like "café" and "té" countable or uncountable (and does it matter)?
• Are these usages the same as the usages in English (i.e., shortened forms of "una taza de café" and "Una taza de té")? Are there any notable exceptions?
• Can we use "dos cafés" and "tres tés" to refer to "two cups of coffee" and "three cups of tea"?
• Can we use "unos cafés" and "unos tés" to refer to "some coffees" and "some teas"?
• Can these be generalized to other nouns about liquids?

Thanks!