Apple Watch 6 battery draining fast

In addiction to what fireyjack said, if the battery drains too fast after an update, see all the replies to:

Update 6.2.1 Battery Draining Too Quickly… - Apple Community

FWIW, in some cases, unpairing the watch, completely erasing it, then pairing and restoring the backup will resolve the battery draining issue after an update.

Batteries - Maximizing Performance - Apple

5 Reasons Your Apple Watch Series 6 Battery Could Be Draining Fast.

• Do you have a cellular model? If so, when cellular data is turned on with the Apple Watch it can drain quite a bit of battery.

• Your battery could also be draining due to apps open in the background. To close them, push the side button next to the Digital Crown to open up the dock, then swipe left on the apps to close them.

• Battery shortage could be caused by the Always On Display and the brightness of the Apple Watch. It can all be managed in Settings — Display & Brightness — Always On (toggle off). From there you can manage the brightness with the brightness slider.

• Wake on Wrist Raise. When this setting is on, it takes up a bit of battery due to using the in built sensors of the Apple Watch constantly detecting when you are raising your wrist in order to turn on the display. To turn it off, go to Settings — General — Wake Screen — Wake on Wrist Raise (turn off).

• Applications. If your Apple Watch has lots of apps and a lot are open in the dock, it takes up quite a bit of storage and RAM putting a bit of pressure on the Apple Watch.

Zodian8

PS:: If your Apple Watch is still experiencing battery drainage, contact Apple Support: https://support.apple.com/