I believe several hotels now have gymns but a certainly fairly well equipped one is at the Celay Hotel which is uphill of the Ovacik 2nd road behind Express Supermarket (which is next to the Milky Way hotel)- about half way along that road.
The owners Celal & Ayten gladly welcome non-residents. They also have a Jacuzzi!
I'm not a shareholder but we know the hotel well!