Enter "Excellent" as a code at the options screen.
Go to the Dunk Contest and select "Legendary Skills" as your difficulty when you face one person (you might wanna change the rules so that there is only one dunk per round because that will speed it up alot). If you win and get lots of good scores in the making, then you will get around 250 sp points. Retry this trick as many times as neccesary.
(supplied by: DarkGoku)