For me too, a FACTORY RESET solved the issue, so it's definitely the way to go.
I discovered it was the Bluetooth module which was causing the issue and for some reason it started to malfunction over time thus the watch needed to be reset to the factory settings and that fixed the problem. I tried restarting, removing/disabling apps and watch face apps, but none of that worked for me. It was the BT module that was draining the battery. My smartwatch was constantly losing connection and freezing occasionally and it turned out it was the BT module that was draining the battery while trying to reconnect.
Once you've done the factory reset all should be fine, at least it is for me, and the watch works like brand new. I easily get up to 4 full days on a single charge and sometimes even more. I do NOT recommend disabling automatic updates though as you should keep your apps updated for security and compatibility reasons. It's unlikely there's any particular app like Samsung Health or Spotify, or watch face that can drain your battery excessively unless you know for sure one of them is the culprit and you should be able to see that in the Samsung Wear app on your phone. Still, you should try not to overload your watch by installing too many 3rd party apps and definitely not all of them at once. Try installing one app at a time if you really need it and monitor your battery usage in the Samsung Wear app on your phone for some time.
There's also an excellent 3rd party app that monitors the watch battery and it's called BATTERY GRAPH. The app runs in the background (with minimal battery consumption) and takes records of your watch battery level every 10 minutes. You can see your battery usage in a very useful graph up to 72 hours back. Ideally, the graph should look like a smooth line slowly going down without any sudden drops unless there's something that drains your battery excessively. I found this app extremely useful and I recommend installing it if you have any battery draining issues. Note, the Battery Graph app will not tell you which apps or watch faces drain your battery, you'll still need to check the Samsung Wear app to find out, but at least it can help you to pinpoint the issue.
