That's one option. But Sandwiches' is valid too, as it ends in an s and is a proper noun, it's not exclusive to plurals. AP style guide for example requires it (and got a lot of flack when 's was proposed as acceptable).
Plus sandwiches itself is a singular noun which is a plural word, so it's s' not s's for most cases there.
Anyway, grammar is weird.
I think it may 100% depend on alcohol and/or THC intake, both of the person writing it and the person reading it. I believe those are the accepted rules as written in both the New York Writing Style Guide and the Chicago Writing Style Guide.
I believe it fits under the section titled As the mood strikes; grammar's mishaps's and bewilderment