Thank you for participating in Watch 4 Beta and reporting your issue. Battery drain issue has been reported by other users. You can also submit an error report through the Samsung Members app: Samsung Members app -> Beta Feedback -> Error Reports to help us debug the issue. We apologize for the inconvenience.
In addition to this, there are other things you can do to increase performance on the battery, like turning off other potentially unused functions and keeping your software up to date. Helpful information, steps, and tips can be found in this guide: https://www.samsung.com/us/support/troubleshooting/TSG01003232/
