Sonic's Secrets: Crusader of Centy.

Free Money.

Enter Rafflesia School and go to the beginners course. There are 4 Coins in the tall grass, cut the grass down to find it. Then go up the screen and hit the right switch to reveal 6 More coins.

Now leave the school, back to the Map screen, re-enter and repeat as many times as you like for plenty of free cash.