If you want to sound like a native speaker, "Any is fine" will do. But if you want to be grammatically correct, "Any one of them is fine" works better but is clunkier. edit: All of the statements work but the two I recommend work best in my opinion.

I would say that all of these are acceptable sentences to say. Of these options, I am more likely to say "Any of them is fine." However if there is no preference amongst the options, you are more likely to hear someone respond as such: "I don't care which one." "I have no preference." "It doesn't matter."