Basically, leafly is a strain-finder. Plug in what qualities you prefer your weed high to have, and leafly churns out strains reported to give the desired effect. That link in my post is an already-made search using only the search parameter "Effect: sleepy." Feel free to use the drop-down menus to tweak your own search(es). Personally, I love the site.
I have tried pretty much every strain available in local dispensaries and by far and constantly the best strain for sleep is "LA Confidential".
Totally narcotic high. For me at least.