A drama with a complicated enough plot but generally quiet ie mostly talking no action does it for me. But I need to be sleepy in the first place, such that I could probably just go to bed without tv and also sleep!
Forensic Files is the best for this if you aren't negatively affected by the content. Peter Thomas had an incredible voice.
How It Works and Ancient Aliens do the job for me. If I watch either of those after I've just had dinner I don't stand a chance. I'm knocked out by the end of the episode.
I use the trashy aliens docs on amazon prime.
the "customers also watched" has been great for discovering all sorts of wackado theories on human origins.