Atomic coffee is really powerful, but not 6 days powerful (more like 8 hours of sleep per sip).
Try taking ambien, downing an entire bottle of cough syrup (the regular one, not non-drowsy), biking for a longer while or take a dose of meth. Yes, meth - it reduces fatigue at first, but then gives it all back with a big extra.
If nothing works, debug menu has the answer: bind debug menu by going ?->1, finding debug menu entry and binding it to some unused key.
Then open the debug menu, find entry for NPC/player edit tool (I think ‘d’), select yourself, pick “edit needs” and check your exact fatigue.
If you retry the check for fatigue in 1-2 hours and nothing changes, there may be some bug somewhere that is causing it, otherwise it may be something you’re using or eating.