Place the trash can as close to the burnt-out, cooled-down charcoal as possible. Sweep the charcoal pieces into a dustpan. Empty the pan in the trash can. Sweep up as much charcoal dust as possible.
Pour two to three drops of dish soap into a mop bucket. Fill the bucket halfway with water.
Dip the sponge into the soapy water. Wipe down the surface where the charcoal burned until clean. Rinse the sponge with water and dip it in the bucket as needed. Let the surface air dry.
Throw away the sponge. Tie closed the garbage bag containing the charcoal. Pick it up, keeping one hand on the bottom of the bag to prevent it from falling apart. Place the trash bag in an outdoor trash can for pickup.