You should make it so that when you shoot the mustard, a yellow stain appears where it was sitting
I also thought about this. Would require a custom surfaceprop. So if you shoot it, it will splat out some mustard.
But i think it takes to much time to do it, time that could be used for other, more important things.
So i say, the mustard- and ketchuptube are allready empty, course of the overwelmning popularity of the Hot-Dogs.