There are a few mods that let the player perform all sort of actions and poses but I never found one that offered only what I needed with a minimum of clutter. Therefore, I put this together for myself and here it is. It adds a single lesser power that let you chose between sitting, meditating and sleeping anywhere. Incidentally, maybe the most interesting feature is the ability to actually conjure the sleep menu at any location whatsoever (ground, bench, even beds why not) with sleeping animation.
The lesser power skillbook titled "How to Sit, Sleep and Meditate" and which can be found in the renting room of the Sleeping Giant in Riverwood. Alternativelly, the power can be added manually using the console command "player.addspell xx0012c7" where xx is the mod load order.

-Sitting regenerate stamina quickly.
-Meditating regenerate magicka quickly.
-Sleeping (Laying down) prompts the sleep menu enabling one to get rested (as required by most basic need mod)

Note: All animations can be interrupted by jumping once (which would play the normal exit animation), or by jumping frenetically to break the animation and exit even faster. Being hit will interrupt most animations. In some rare occasion, the exit animation does not play and the player gets up almost instantly, but without further consequences.

Should work with anything. No vanilla form were edited.