Not very immersive (I doubt you’d have enough air in your pack to sleep on the surface of Mars for 8 hours for example), but this adds a sleeping bag you can drop to sleep anywhere.
You will get an item “My Sleeping Bag” when the mod installs. You can find it in your inventory under Apparel. Just drop it on the ground to use it, then use the R key to roll it up when you are done. Romanced companions will use it as well.
If you don’t get the sleeping bag, or forget to pick it up, you can use console:
First find the form ID:
help psb 0 armo
Then add it to your inventory:
player.additem <formid>
Requires: Plugins.txt Enabler
Credits:
Aurelianis