Im looking for fics where spike is the only one to figure out that's not buffy in the body swap episode while everyone else doesn't

Here are some.

Like Warm Champagne by Slaymesoftly

http://spikeluver.com/SpuffyRealm/viewstory.php?sid=8247

Summary: My take on what might have happened when Faith switched bodies with Buffy.
Complete

He Knew by Tista

http://spikeluver.com/SpuffyRealm/viewstory.php?sid=1567

Summary: Takes place after Who Are You in the 4th Season. Spike confronts Buffy after he runs into Faith in Buffy's body. Complete

A Change of Heart by my_perfect_muse

http://spikeluver.com/SpuffyRealm/viewstory.php?sid=28443

Summary: A body switch based story. It's a one-shot atm but may turn into more in the future. What would have happened if Spike had been the one to tell him about Buffy acting strange? What would Buffy do and say after finding out? Complete

those are good one's but i feel like there are more out there...

This one's available through the Wayback Machine.

Normal by Kari Mouke

Summary: Angel said normal. Buffy gives it a try and fails horribly. Spike comes along and helps her to discover exactly what normal means for a supernatural creature like herself.

I did a search on SR with the words body and switch in the summaries.

That is all the ones that came up that were related to the episode.

Maybe there are more but those were all could find here.

I have been reading a fic which fits into your request. It's by sweetprincipale over at ff.net

Sex and Candy

Summary: Set during S.4, episode Who are You? and deviates from there. Riley's unintentional infidelity creates a chain reaction. One act of camaraderie sparks one night of passion between Spike and Buffy. Will be short and smutty. Please read and review. Rated M. Has three sequals.

Forsaking Most Others by brutti_ma_buoni over on livejournal. It's part of her Green Card verse series.