Grenades are explosives that are either used by Joshtick or StAddison in battle. When wielded by StAddison, they create a massive flash that stuns anyone. When wielded by Joshtick, they actually blow up to deal damage. They appeared in the movie and the game, but never made it to Slush Tile Rush.
Slush Invaders (movie)
When StAddison cleared the elevator area of Drabs, he launched a stun grenade which blinded/disabled them temporarily. As Joshtick, however traveled to rescue Standrew from captivity, along with Westick and Stick JK, he threw a decoy bomb, then blasted the door open, throwing a bomb onto a Drab's face and kicking the drab into another group of drabs.
Slush Invaders: Game
StAddison has the ability to throw stun grenades as his input attack. His Double Flash upgrade allows him to stun enemies for 4 seconds.
Joshtick, on the other hand throws small grenades which explode once in contact with the enemy. His Cluster Grenade upgrade enhances this ability, so that Joshtick does not just throw one grenade, but 3 at a time.