I thought perhaps you cake-decorating gurus might have a suggestion as to what we can make these pearls out of...

I need a costume prop strand of pearls that look somewhat real, but when pulled off another performer's neck, can be easily powdered/crushed under a boot, and then will subsequently dissolve with water.

The performance venue is outside and gets a daily spraying with a water truck, so clean-up would then be minimal, but as this is happening in a public area, it needs to crush/powder easily when walked over, both for the sake of the stunt as well as for the safety of the general public (we don't want someone sliding/tripping over a stray pearl).  So the conclusion we have come to is that it should be made of something...sugary? Which is why we've come to you, oh cake decorating gurus of the world, who can seemingly make ANYTHING out of sugar.

We are willing to make these pearls ourselves, or, if too difficult for beginners like us, we are happy for any suggestion as to where we might find something like this? What should we be looking for? Is fondant too squishy for this project? If it hardens, will it crush easily? Any other materials/ingredient suggestions are welcome. 

Please help! :-)

You can mold table sugar into spheres [google sugar molding].  You'd need to try to lay in the string as you went along.  You could mold fondant and dehydrate them [that's they only way they'd dry enough to go to powder when crushed] in an oven with the light on [likely for a very long time]. 

good luck