For me, it would have to be something nice, but not so interesting that I want to stay awake (Ariadne auf Naxos). Or something I’ve heard a million times (The Magic Flute).
Beethoven has always been calming for me, so maybe Fidelio too.
If you’re looking for beautiful music, maybe Tosca or Rusalka.
There are others that I wouldn’t necessarily fall asleep to, like Don Carlo, Pagliacci, Rigoletto, or La Traviata. This is a pretty good list of some of the best known operas.
And wealthy or well-connected. If you’re poor, you don’t necessarily have much of a chance.
The link is a long read, but interesting. The story of Cameron Todd Willingham, who was executed in Texas in 2004 for supposedly setting a fire that killed his three kids.