Now, we all know we can’t use a double negative in English; just as in math, two negatives become a positive.  In order to avoid that double negative, we often employ “any” or its derivatives.

I don’t want anything.
I haven’t made any decisions yet.
I wasn’t doing anything special.
I don’t know anyone who could answer that.

“Any” has another use, however, in affirmative sentences: to represent something that is undefined.  Its translation into Spanish is usually via the subjunctive or “cualquiera”.

I’ll give you anything you want (lo que quieras).
I’d rather listen to anything else (cualquier otra cosa).
Jeffery will go anywhere his favorite band goes (irá adonde sea).

So, “any” in negative sentences (ningún) or in affirmative sentences (cualquier)