Allison Sheridan from the Nosillacast podcast has been experiencing a similar behavior on her M1 Max MacbookPro. She basically is on a year-long crusade to find the root cause for this battery drain.
She has documented her experiences on her podcast and her blog - here is a list of the blog posts involved, including extensive support experiences with Apple and a lot of debugging - and even buying a new MacBook Air M2 to get rid of the issue.
https://www.podfeet.com/blog/?s=battery+drain
Her most recent post:
She was able to finally get it to stop. She still is not 100% sure what was going on, but one thing that may or may not be of interest:
For my next test, I needed to let iCloud finish downloading all of my photos. As I’ve mentioned, this is the Mac on which I keep all of my full-resolution photos. I was taught years ago by an Apple Senior Advisor that the fastest way to get them down is to start from scratch and download originals. If you let it download optimized images first, and then change to full-resolution, iCloud has to check every single photo one at a time to see if it’s full resolution. Back when I had around 75K photos, it would take 3.5 weeks to bring them down after optimized were already there. Apple said that was normal and to be expected. I flipped the switch to download full-resolution images, plugged it into power, and changed the battery setting to force it to stay awake. (…) The entire download took about a day and a half and it was ready to run another sleep test. I started the test at 8:36 AM and finished at 6:16, so just under 10 hours, and in that time span it lost, drumroll please … 0%. It stayed solid at 100% for 10 hours.
These days, all the syncing going on is a challenge…
I have a MacBook Air M2, too. Fortunately, it does not really drain its battery when sleeping. I can have it sitting there for days without significant battery drain when sleeping.