Can't seem to find this fic I know I read it on Elysian Fields and all I can remember is spike works at a coffee shop and Buffy is a popstar with Giles as her manager.

Any chance it’s Pictures of You by kats_meow? https://dark-solace.org/elysian/viewstory.php?sid=6128
I’m pretty sure one of the earlier “jump” scenarios have her as a Country Star with Spike as her former writer/partner/lover.

Sounds like "Beyond the Sea", the story that I believe Sunalso took down in order to file off the serial numbers and publish as original fiction. Someone on EF might have a copy saved.