Watch series 11 battery drains quickly
New series 11 watch. Fully charged in morning. Ride to work for 20 minutes using the fitness app. When I get to work battery is less than 10%
Apple Watch Series 7, watchOS 11
Did you already try to force restart your iPhone and Apple Watch?
Force restart iPhone - Apple Support
To force restart your watch, press and hold the Digital Crown and the Side button together for about 10sec, until the Apple logo comes back again.
If this does not stop the battery drain, erasing the watch and paring it again helped users in the past.