It is normal for notebook computers to use some power during sleep. Sleep only reduces functions to a very reduced level. It it does not turn everything off. In adding to preserving parameter data (startup volume info, contents of RAM. etc), sleep must allow, at least on Macs, the running of automated self-maintenance scripts in the small hours of the morning.
Some browsers may continue to exchange data during sleep. "Phone home" apps will also. Many complaints like yours are due to unneeded third-party apps like anti-virus, so-called "cleaning" apps, and client side VPNs (the ones with scare adverts all over the TV.) If you have installed any of those, this is a self-inflicted wound.
"Health" is a ROUGH measurement of battery WEAR. All rechargeable batteries have a finite service life, degrading over time. Health is the battery's current capacity when fully charge divided by the DESIGN capacity. The latter is ineact, being an average new capacity of all batteries of one model. Average means some batteries will have a higher of lower value for actual new capacity but the number used for calculations is an AVERAGE.
Heath fall-off with time is blatantly non-linear. This chart from the Coconut Battery app and my Macbook Pro shows how health goes up and down over time. The battery was just over 9 year old at the time the chart was imaged and represents about 16 months of Health readings:
Note that between 22 May 2022 and 25 June 2022, health plummeted almost 10 percent but then recovered recovered. Today the battery is nearly 11 years old and still, shows 83% health. The computer still has acceptable battery runtime for my needs and has no useless fearware install that would further tax the system and battery,
Having with this subject for a very long time, I've concluded that "Health" exists for one reason: warranty. Apple states that if Health falls below 80% while the batter show les that 100 cycles during an Apple warranty period, the wil consider a warrenty reacedment of the battery. I se not other need for such an inexact and non-lunear value to exist.
Testing your own computer is easy.
1) fully charge it.
2) completely remove ALL anti-virus, "cleaning," VPN apps, battery managers, or torrent software
3) Quit all user apps
4) Make sure the lid is full closed.
5) go to bed
6) check it the next morning
If I do that with my Macbook Pro, the charge is usually still over 90% under those conditions.
If the massive drain still shows the next morning, post back. There is one step more you can do for testing before taking it to Apple for evaluation.
