**Any** is very often used with uncountable nouns and plural nouns. It can have the same kind of meaning as the indefinite article **a/an** has with singular countable nouns. 
E.g.: I  haven't got a car, and I haven't got any money to buy one.

Is there a tin-opener in the house? And are there any plates?

With this meaning **any** is unusual with singular countable nouns.

She hasn't got **a** job. - **NOT**, She hasn't got **any** job.

Do you know **a** good doctor? - **NOT**, Do you know **any** good doctor?

*With an uncountable noun or plural noun, **any** usually suggests the idea of an indefinite amount or indefinite number.*  When there is no idea of quantity or number, **no article** is used.

Is there any water in that can?

Is there water on the moon?

**Any** can be used to emphasise the idea of 'free choice', with the meaning of 'it doesn't matter who/which/what'. With this meaning, **any**is common in affirmative clauses as well as questions and negatives, and is often used with singular countable nouns as well as uncountables and plurals.