u/Material-Dot7684

This is by far my most pedantic pet peeve as we seem to have just accepted it in the era where many just go to Starbucks.

That being said, coffee is a liquid, you can't count it. You need a unit of measurement there. You can have a cup of coffee, a medium coffee, a large coffee, 16ozs of coffee etc. But you cannot have one coffee unless you mean the beans in which case for clarity it would probably be best to say one coffee bean. ​