Why do you need to ask them specifically to code fizzbuzz? There's nothing magical about it and it's a condescending coding exercise.
Ask stuff about their everyday coding and their favourite language. What's the difference between an Array and a Set (in your language of choice). How do you add an element to those? (if it's your day to day language you should remember, right?)
Tell me about an issue you had to debug. Tell me how (something) works in general. Something basic, no need to go into much detail, but just to see if they get the basic idea and have used it.
Again, who cares about fizzbuzz when you can ask them about http headers, network delays, etc (it will be more job relevant as well). People who can't code fizzbuzz will usually fall flat on those questions as well.