When you are doing a cup, remove your memory card and do the cup. When you have won the cup, you will get a lot of money. Then, go to the shop and buy anything. When you have selected what you want to buy, insert your memory card again and save what you have bought. The cup that you won will not be saved. Restart the game and the cup you have just won will be gone, but the item that you bought will still be there. Do the cup again and to get a lot of money again.