This mod let you sleep using inventory menu, all you have to do is to click on "sleeping bag" and a new menu will popup. It's very simple and you dont need to buy the sleep bag from trader, when the game start you will see your sleeping bag. NEW GAME REQUIRED!
This mod is not from me. It´s from Speed aka LW. . I found it in an old forum after I was so sick of sleepless nights in the zone. But I wanted the game mostly unmodded. It adds only the sleeping bag and works for SoC version 1.0006. Attention, a new game is required.
Good sleeping Stalker!