I'm going to be running a science workshop for kids, where kids build a "ballistic reentry vehicle" out of a cardstock paper, holding cookies inside it. The kids will be dropping the vehicle from a height of about 6ft. The kids will be designing the box in such a way as to keep the cookies from breaking.
I'm looking for a type of cookie that breaks easily when dropped from such a height. I'd prefer not to bake the cookies myself if I can avoid it. I just need to know what kind of cookies I can buy from a store that are most likely to break apart into multiple pieces when dropped. I imagine the cookies would have to be brittle, but I don't know what kinds of cookies tend to be the most brittle that would be readily/cheaply available in a store. I think most cookies are made to retain their shape rather well, but I'm sure some types are more breakable than others. I would prefer cookies that fracture and break apart into multiple pieces easily when dropped, not cookies that simply fracture or flake off the surface.
What kind of cookie breaks easily into multiple pieces when dropped? If I had to bake the cookies myself, what would I have to do to ensure that they come out brittle and easily breakable? Without buying and testing all kinds of cookies to find the the right kind, what properties of the cookie should I look for (e.g. ingredients, style of cookie, etc...) that increase the likelyhood of it being easily breakable?