This is an intermediate level activity, but I have simplified it where even younger toddlers can enjoy it .
This develops OCCI, order, concentration, coordination, independence, judgement.
Develops care of self, fine motor control, wrist and eye-hand coordination.
A loved it so much she felt she needed to give it a hug after it was all clean! I could have added a bit of chocolate syrup and smear it over and have her clean that next time. Water or a diluted vinegar and water mixture can be used as a simple cleaning agent.