Buffy and Spike traped in pocket dimension.

I'm lookin for a story I once read were the bad guy gives Buffy a bottle of sunscreen and when she finally opens it it's supposed to transport her to a pocket dimension. Somehow Spike gets traped with her. The place is like a beach with a house. Somehow Spike can go out in the sun. However the dimension was only created to support one person and the addition of Spike makes it less stable.

I think you are after Instant Sun by verity watson.

That is totally it! Thank you so much do you know if she ever posted the sequel?

I haven't seen it if she did.