Two I found for you. The first one will end as you asked, not sure about the second but it looked fun, haven't read it yet! Enjoy!
Fading World by Absenteye26
Set in S6 episode 'Normal Again'. Both Spike and Buffy are stung by the demon, and end up in the same mental institution. The Glargh...Glush...um, the demon has a bit more power in this fic, so Spike and Buffy fall into a coma...a permanent stay in the mental institution.
http://www.bloodshedverse.com/stories.php?go=all&no=2129Not So 'Normal Again' by greenhair00128
My own spin on 'Normal Again.' Instead of an institution, Buffy's alternate reality seems to be an almost normal, happy life, complete with a white picket fence and a not so un-dead hubby!
http://www.bloodshedverse.com/stories.php?go=chapters&no=3129