Hmmm. I don't know. Breaking on cue isn't that reliable. You could try making a cup from one of the soft clays (Super Sculpey in the box comes to mind.) I would make it intact, bake it, break it by hand deliberately, then reassemble it with some kind of weak glue so if dropped the glue wouldn't hold. The problem is that just holding it would probably lead to that breakage, and it certainly wouldn't sound right hitting the ground. So I am not sure how to make this work. /sorry.