Most people don't realize that Macs wake up a lot when they are sleeping. Some apps tend to check for updates all the time....Google Chrome is one of the most worst offenders. Make sure Power Nap is off in the System Settings (assuming Power Nap is still an option).
Most times when I assist people with locating the source of battery drain over night when the laptop is supposed to be asleep......most times it is due to some cloud file syncing service such as iCloud. You can try disconnecting the laptop from the network to see if that makes any difference (if you are only using WiFi, then just click the WiFi icon on the menu bar & move the WiFi slider to the off position). If disconnecting the laptop from the network helps with the battery drain, then you know some app is either updating resources or syncing files. The trick is to figure out which one(s).
You can also try creating a new macOS user account. Log out of the main user account & log into the new user account. See what happens overnight. If the new user account does not have the battery drain, then you know some configuration within your main user account is at fault. Just make sure:
- Do NOT sign into AppleID or iCloud
- Do NOT restore from a backup.
Another thing to consider......is the laptop actually entering sleep mode. Sometimes an app or process can prevent a Mac from sleeping, logging out, or even shutting down.
Have you tried a simple reboot of the laptop? Sometimes this can work miracles.
Make sure macOS Sonoma is completely up to date...I believe 14.3.1 is the most recent version.