Try the Sonos Controller App, which does work on my iPhone, although i don’t use it bc my Sonos is integrated into the Harmony App universal controller, which if you have it, you’re set. The Harmony App, though, requires buying a Harmony Hub, so there’s that.
If the Sonos Controller can be found inside the Apple Watch App (after downloading it your phone first), you should be able to get a version on your Watch. Let us know if this works.