Can one make bread or pastry out of coffee. They can be added to flour, but one can’t make them into anything that one could confuse with bread. Corn and rice (and quinoa) can be turned into bread or cakes. Coffee and cocoa are just flavorings.
Of course then you into a discussion of why potatos are allowed, though when you make a flour from it, it is only “bedievad” that it can be turned into bread of cakes, whereas corn can be used to make passable bread and cakes.