With your dollar, hand it to one of the budding entrepreneurs in your neighborhood and buy your self a glass of lemonade!
It is a cliche but this was my very first business as a child. For me it is never about the actual lemonade, it is about encouraging kids. Think about it - they are outside, not inside on a computer. They also have a new level of responsibility and that helps them grow. They get to answer questions and engage with adults which is a good thing.
Just today I bought some and I could not believe what I pulled off. There were three girls, all sisters. I told them I wanted to see if I could guess how old they were. They were up for it but laughed at the idea of this stranger trying such a thing. I pointed at the oldest, scratched my chin and said, "I think you are ten years old." I got it right and they were shocked - one turned in a circle - and could not believe such a thing was possible. Now they were standing on the balls of their feet. I turned to the next oldest and said, "I think you are eight years old." All three of them said, "YESSSS! YESSSS!!! OH MY GOSH - YESSS!!!" They were all pulling for me now. The youngest came out from behind the table so I could better guess because she was next. "I think you are six years old." They about flipped, "OHMYGOSHHH!!! YES!!! SHE IS SIX!!!!"