You could go around the neighborhood and ask if people want you to get payed to wash their cars. Be prepared because some people want you to bring your own washing supplies.
Create a cold drink stand out of a fold-up table and a home made sign. You could sell lemonade,soda,water or Brutan juice (a gatorade and SunnyD mixed together that I made with a friend). You also can’t sell it to expensive or people won’t buy it.