Just some days ago I saw a video of Linus Tech Tips about battery-draining standby modes of Windows laptops (and sometimes MacBooks).

Now I came across Sleep Aid (via Michael Tsai), a macOS tool to diagnose and solve standby aka. sleeping issues on Macs. From the blog post Hot Bag MacBook about it:

Have you ever travelled somewhere to find that your MacBook is nice and warm, with next to no battery left? If so, these are the common causes of a „Hot Bag MacBook“ that we‘ve found so far.

This could be handy.