Have you done all of these steps already?
According to the walkthrough:
Get the keys for the truck: Remember the truck with a dirty windshield by the village gate.
Go to Toni's house. Check the pot of soapy water above the stove.
Use the sponge from Wenzel's bathroom on the soapy water to get wet sponge. It will automatically be in inventory.
Go to the village gate. Use the wet sponge on the dirty windshield of the truck.
Look through the windshield and see: pink leatherette seats, puppet pirouetting and the name Sugarpuff.
Go back to the alley and talk to Hannek about keys.