This would be an item a Hedgehog would throw along the ground (perhaps throw it across a short arc through the air before it starts moving along the ground), and the ground it touches would get coated in a white foamy streak.

What would happen is the "soapy" ground would become slippery, making it hazardous to move across or stand/land on. Basically think of how ice acts in various platformer games, where the character continues skidding in the direction they were moving even when the player stops pressing the movement key. Also, any ground at more than a 45 degree slope that gets soaped up becomes impossible to stand on; any hedgehog that is currently standing on it or lands on it slides down the slope, and if a hedgehog attempts to walk up it, they'll only make it a short distance up before sliding back down.

I'm not sure if the soap should stay until the ground is destroyed, or if it should wear off after a certain number of turns... perhaps this is something that could be tweaked over time, based on how powerful the soap seems to be (i.e. start out with it only going away by destroying terrain, and if it seems really overpowered, make it wear off after 2-3 turns).

While this would primarily be a defensive weapon (soap up the ground around you to keep enemy hedgehogs from walking up and dropping unpleasant things on your head), I could see a great offensive use: if an enemy hedgehog is perched on a precarious piece of land near the edge of the map that you're having a hard time hitting directly, lob the soap his way, and watch him slide off and take a drink