paper shopping bags
transparent sticky tape
large round plastic lids
What should be done:
1. Fold inwards the flap of the box, to strengthen its sides.
2. Cover the box with paper bags with adhesive tape.
3. Encourage children, that they paint the boxes with details that make them look like a car: white headlights, red taillights, license plates etc..
4. Use the plastic cover as a steering wheel, before cutting a few holes in it.
What else can be done:
On the sides, attach cardboard wings, making the box look like an airplane. By attaching more boxes, you can build a bus.