This doesn’t look like a story. How could anyone write a sequel to it?

From what I’ve seen, sequels aren’t necessarily direct sequels on this site. I’ve seen settings visited from other points of view. Perhaps the hospital rooms after various people eat these sandwiches, or a confrontation between father and daughter over being accepted in society.

It’s just limited by your own creativity, really. The way you approach the problem. And I’d also remind you that the site isn’t limited to sequels. A prequel about the developers of the sandwich could be interesting, no?