I think a nice sort of ammo, to get to your friends, is water and flower. Take a big bore at least 1 inch, put e small water ballon in it, and a few onces of flower. Put a piece of toiletpaper in it as a stopper, to prevent the flower to fall out. When loading, first put in the water ballon, so it prevents the flower to slip into the valve.
When shot at a fair pressure, the ballon will pop, and a mass of flower and water will shoot at the target,making it all wet and sticky
You could uwe powdered sugar to makle is extra sticky. Haven't tried it yet, but I think it would give an amazing result.