After last update Apple Watch series 4 battery drains quickly

If the battery drains too fast after an update, see all the replies to:

Battery Drain since watchos 7.4 - Apple Community

WatchOS 7.5 battery drain - 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. (Simply unpairing and pairing again may not work.)

Unpair and erase your Apple Watch - Apple Support

Also, some people have found that simply waiting a few days after an update resolves the battery draining problem.

After update 8.4.1 batter drains in 5 hours. Stopped all app refresh and cleaned out unnecessary apps. Did a reset, unpaired and paired. Erased and restored. Still draining fast, this happened after the update. Nothing has worked so far and it’s aggravating. My watch was working fine before this update!

I have an Apple Watch SE and I am having the exact same problem. My watch was fine and although I usually charge it ever night it could go about 2 - 2 1/2 days on a charge. After the most recent update last week (around 2/8/22) my watch is out of charge by NOON! It was fully charged when I put it on this morning at 6 am and now here it is, less than 3 hours later, and it is down to 38%. I did notice that all my apps were turned on for background refresh yesterday (I guess the update did that because I usually have almost everything turned off) but even after turning it all back off and charging overnight I am still having the same problem. My watch is barely a year old (warranty expires tomorrow...figures!) and the watch says my battery can charge up to 100% so that doesn't appear to be the problem. I hadn't put any new apps on it or changed any settings so it has to be the update that did this. Very frustrating! Have started the process of unpairing and pairing the watch to see if that helps.