To enter the cheats, start any game, pause it and go into the
optionscreen. Now enter the cheats. After you are finished,
leave the game. In the optionscreen of the main menu you can
now enable the cheats!

Invisible Walls       BBBZAAAZ
Curve Ball            ZABABB
Crazy Ball            BAZBBZAB
Super Power           ZAZZZZZZZZ
Super Goalie          AAAAAZZZZZ
Super Offense         AAAAAZB
Super Defense         ZZZZZBZ
Sudden Death playoffs AZABAZ
Stupid Team           AZBAZB
Dream Team            AAZZBBAA