There's an "indoor cycle" workout but you probably need a third party app and gear to be totally satisfied with it or quantity anything beyond that time and heart rate.
As an avid mountain biker I can only see indoor cycling as exercise time and where you can work to be in heart rate zones - not ways to compare it to a real ride. I've used the Abvio app (Cyclemeter and all their apps are same, just default to one exercise) before the watch. It might satisfy you are looking for more data. I chose it over some solutions because you can sync to Strava if you want or keep you data private.
On indoor distance, I have associates who go to indoor cycling studios and they somehow quantify their rides based on what's shown on the screen. They all have Garmin watches and review their rides on a web site.
On cycling and activity, know that a wrist HRM - any of them - might not be good enough to satisfy all users. The Apple watch itself or your phone with apps can connect to chest and arm strap HRM units. My triathlete friends do that whether they have an Apple or Garmin watch.