Battery Draining with IOS 16

I am experiencing the same thing after update from 15 to 16.3.1. At the same time watch is also completely useless 9.3.1. Whereas with prior os for both I got to bedtime with plenty of juice; 40-50% left on the watch and 30+% on phone depending on usage. Now, watch is lucky to last until dinner before giving low battery warning and on several occasions has completely died. Phone requires charging once or twice a day. Phone has 91% battery health and is 16 month old 13mini. Watch is 6 cellular with almost no cellular use but I bought and paired a brand new watch8 which for the first 3 days has been behaving just like the watch 6 was. I have done multiple soft resets on phone. Unpaired and set up old watch as a new device, reset network settings on devices and even turned off watch for a day to see if something in the connection was driving it. Nothing worked and apple is totally useless. Even after escalating with tech support their best advice was to get new batteries. I tried the new watch with 100% battery health to no avail. Obviously, that will be returned. Might just go back to my $10 Casio which goes about 10 years on one battery. I don’t mind nightly charging but watch must last a day. Any words of wisdom would be helpful. No idea what to do about phone…

Try a Forced Restart, it resolves many issues.

Force restart iPhone - Apple Support

FWIW, I have an iP13P on iOS 16.3.1 and I am not seeing that issue.