I updated Watch OS 10.5 (21T5571a) on May 1. However, the battery is draining quickly. My watch is an Ultra, and I fully charged it at 1 am. When I woke up at 8 am, the battery was at 79%. By 2:30 pm, the battery was only at 20%. I have not engaged in any activities today.
I just noticed this issue on my Ultra 2 in the last few days, it was almost like my watch would not fully charge while on the charger (even with optimized charging off), and then last night the battery drained from close to 100% down to 77% while sleeping. I'm not sure if it is from one of the beta upgrades or what, but I found a YouTube video that is somewhat of a general solution, but supposedly it has worked for some people complaining about the same thing.
Link to the video: https://www.youtube.com/watch?v=Q1-Td6Su904
I might hold off on the beta upgrades on my Apple Watch until this gets situated, because that battery drain was frustrating!
Watch drained to 0 in one day, no workouts. Currently draining in about 20 hours
My feeling is that this is related to Intent Based Widgets. We could test this by removing all widgets from the watch face and seeing if there's an improvement since many widgets are now Intent based. There's a bug.