GrammarTOP.com

nouns and isn’t used with uncountable nouns:

I would like a sandwich.
I would like some juice. (Not: I would like a juice.)

With uncountable nouns we use the determiners ‘much‘ and ‘little‘:

There isn’t much milk in the bottle.
They have little money.

Making Uncountable Things Countable – Quantity Expressions

Uncountable nouns can be paired with words expressing plural concept. These are words
and phrases like ‘a glass of’, ‘a bottle of’ or ‘a piece of’ or words for containers and
measures. We cannot say ‘an information’ or ‘a music’. But we can say a ‘something’ of.

In short, uncountable nouns can become countable when the noun is in a container. For
example:

some sugar — a bag of sugar
some water — a bottle of water
some cereal — a bowl of cereal

Thus, you can’t say ‘two waters’ but you can say ‘two bottles of water’.

Try to drink at least eight glasses of water each day.
I’d like a glass of water, please.
We bought two bottles of wine.
This is a beautiful piece of music.
I bought you a bar of chocolate.

Note: In informal English, we can say 'a coffee', 'three waters', etc.
with
the meaning 'a cup of coffee', 'three glasses/bottles of water', etc.

Sometimes uncountable nouns are used as countable, to mean ‘a measure of something’ or
‘a type of something’:

Can I have two teas and one coffee, please? (two cups of tea and one cup of coffee
…?)