Juiced Cheats

All cars:
Submit the code PINT at the cheats screen to unlock all cars in arcade and custom modes.

More money:
Submit the code FAST in the pre-release version of the game.

Completion bonuses:
Get a 100% completion in career mode to unlock the prototype mods for all cars in career mode and the Extreme Nitrous Series in Arcade Mode.

All Prototype parts:
Get 1,500 respect points from every CPU character.

Arcade bonuses:
Complete the all the series in Arcade Mode, except the Extreme Nitrous Series, to unlock the Bronze, Silver, and Gold Prototype Challenge Series.

Get Easy Money:
All you have to do is host your own sprint race and set the class to Class 1. You do not have to race, but just bet. Wait for the Viper and Corvette Z06 matchup and bet the max amount of money on the Viper and watch the money roll in.
User Cheat by Nelso_Mower

Host your own race, then pick sprint. Use your own speedway as the track. Select "Watch Race" so that you can bet. T.K. and Biggi will always race against each other. Bet on the car with the higher horsepower. You will win about 98% of the time.

REMEMBER: This trick requires online mode and two memory cards. When you get online, race a friend with the best car, but have a backup on your other memory card. Race your friend repeatedly and intentionally lose. When he has a few of your fixed up cars, have him sell them and bet you the money. Then, have him lose or just ask him for all the cars back and sell them yourself.
User Cheat by Nelso_Mower

For extra money race for pink slips with CPU characters. After beating them and win the car, sell it. Make sure you have more than one car in case you lose.

Race and earn a bit of money, then host sprint races at your won track. Have Class 1 racing, and bet all your money on the Viper. If there are two of the same car, bet on the blue one.

Easy pink slips:
Have your car at 199 with nitro set up a pink slip with tk or who ever wait until the type of match is sprint race them make sure their car is in the 150s-179 cause I lost against a 186 car have fun:)
User Cheat by chico322

Challenge a crew to a pink slip challenge. Remove your memory card before you do it. By doing this, if you lose restart your PlayStation2. After it has loaded, your car should still be there. If you win, go back to the main screen then select "Extras" to enable auto save. Make sure your memory card is inserted as you go in the "Extras" screen.

Get easy wins:
Get three of the CRX mod it until you have 199 hp. Let Amber, Vito, and Chief race the free sprints until they get full skills. Then , use them in a 2-2-2 or a 3-3 circuit race.

Get easy mods:
When you have a certain car you want to upgrade quickly, go to host your own event circuit or point to point Do one lap and your car's horsepower that you want upgraded. Choose to enter the event. Race and bet only if you can win. No matter where you finish, you will unlock a mod each time. Make sure you finish the race. Only do one lap, as it does not take as long. When you have your car fully done, race for pink slips.
User Cheat by Nelso_Mower

More efficient turns:
While you are about to do a turn you must slow your car while entering it. When you are exiting, nitrous out for the best and most accurate results in that turn.

Juiced Official Game Site