An extension from Sonic Adventure 2, Sonic Adventure 2 Battle managed to integrate the Black Market to offer you gifts in exchange for rings won in levels. You can buy fruits, nuts, chao eggs and even menu characters!
This adds more depth to the extent you can raise yer chao. This will help you to improve your chao faster and easier. There is, however, an infinate rings cheat with this addition.
Go to the chao black market with a good amount of rings and buy the most expensive chao hat there. Take it to a chao garden and save the status by exiting. Re-enter and go to the black market with the hat in your hands. Sell it off and recieve about half the amount you payed for it. Don't exit the chao lobby whatever you do! Instead, press 'Reset' on the GameCube to restart the game. When you can, go into the chao garden where you placed the hat and it's still there and you keep the money you sold it for. This is a quick and easy way to obtain a lot of dosh.