Fizzy Caramel Apples -- how are they made

When at a factory outlet mall in Grove City, PA, I purchased some gourmet caramel apples.  One thing struck me, the apples are fizzy in taste.  I have done some searches and the only thing I can find is how to carbonate sliced apples with dry ice.
 
Any ideas?  Or maybe there's a breed of apples that taste this way.
 
Thanks
Steve

Are they fizzy all the way through to the center of the apple, or is the "fizzyness" just at the level of the skin?  If it is just at the skin level, the apples might be coated with something like a powdered fizzy drink mix (or a mixture of powdered citric acid and baking soda) before being dipped in the caramel.