Both never interacted as they're from different game's parts, as Sayaka is from Danganronpa Trigger Happy Havoc while Mikan is from Danganronpa Goodbye Despair. However they do share a interaction in the Ultimate Talent Development Plan.
In UTDP, Sayaka and Mikan talk about Toko's works together. They both seem interested in the books. Mikan later mentions that the heroine from Toko's novel "was the splitting image of Sayaka." Toko seemed surprised and said that the novel was based off her own fantasy, was confused, and asked if she was thinking about another book. Sayaka then says that she is interested in the book that Mikan was talking about, and that she will read it later.
Later, if the player chooses "The haunted house is a classic" before Sayaka's performance (playing as Maizono), she'll check up Mikan's haunted house exhibit. In it, Mikan mentions that Sayaka is the first one who has gone in ever since she took over the reception desk, while smiling at her. Sayaka seemed to enjoy the haunted house and that it helped practice her reactions as a pop sensation. However if the player plays as Mikan, she won't be able on looking for Sayaka while Mikan is in the reception desk from the haunted house.
The "socially awkward character" and "social butterfly character" dynamic is very popular, and it fits them quite well. Due to them not interacting in canon, being from different games, and more, not many people ship it and it is considered a rarepair. It is most likely shipped due to their UTDP events from Danganronpa V3.
Fanwork mostly takes place in AUs since they never interacted in canon. In some fanart, they can also be seen with Toko due to one of their UTDP events. Though, there isn't much fanfiction and fanart out there.