Empty egg cartons are great to turn into boats, trucks, or buses. For example cut the egg carton in half, Sellotape an old paper towel inner to the middle, cut out some paper sails, paint and you have a boat! Or keep the egg carton whole, paint some wheels on it – hey presto, a bus that your toddler can put some of their toys in.
Note – this is not recommended for children with egg allergies. An alternative is using empty tissue boxes.