Trying to find out what is draining the battery on my MacBook Pro
If you have "Find My Mac" enabled, macOS will keep persistent TCP connections even when it "sleeps" (not really sleeps then). This draws battery, sometimes a lot. You can check if it is on with terminal:

pmset -g | grep -i tcp


See if you have:

  tcpkeepalive         1


If it is so, you cannot really do much unles you turn off "Find My Mac" (with all risks that it involves).

Also it is possible that something on your mac prevents it from sleeping. Typically you can find it with pmset -g assertions. It will tell you what keeps your mac awake. Mine, for example, is kept awake by bluetooth keyboard and touchpad all the time. Sometimes there are also processes stuck and keeping my mac awake for no reason. Then I just kill them.

In general, you may keep your macbook on power adapter for most of the time despite people telling you that you should not. I had a number of macbooks in my household since 2007 and almost always kept them on power adapter. In the end they were too old or failed for any reason but never due to battery. The worst battery performance I had was about 75%. Most of them were > 80% capacity after several years.