Here are all the cheats for FIFA 2000. To enable them, simply go to the options menu and scroll over to 'cheats.' There enter the cheats in bold below. You must do this from the menu, not during the game, you can't turn them on or off during the game.

LIGHTSOUT - Glow Mode
BURNABY - EAC Pitch
SIZZLE - Lightning Mode
MOMONEY - Unlimited Bankroll
DIZZY - Alien Mode
HOOLIGAN - Bonus Teams

Check out some examples of what the cheats look like here.