Select options at the main menu. Click on player profile, and click the "Cheats" option. Enter the following.
!MegaWedge!
All Sponsors
To unlock all in-game sponsors, head to the cheat screen and put in (case-sensitive) uDunGud as a password.
All Tracks
To unlock all of the game's tracks, simply type in the cheat "TraxAhoy" on the cheats menu.
Chimera
Finish P2P with the truck on expert difficulty.
Fast Easy Back Flips/Frunt Flips
This isnt exactly a cheat but if you ever try to pull off the back flip or frunt flip they always take a long time to rotate well if you double tap the direction of the flip it will go twice as fast then you can pull off a double or triple back flip.
Fireball
Finish the P2P with bike on expert difficulty.
Free Freestlye
This code works for any atv or bike, as well as any free style track.As soon as you start the freestyle you're in last place. The easiest way to make your points increase is to pulla wheeley. hold the wheeley as long as you can even through the jumps. when you pull the wheeley it counts as one trick, you then hit the first jump keep the wheeley and pull a trick (backflip/tsunami) you now have x3 points. Be sure to pull diferant tricks for each jump to increase your multiplier. Also hold the wheeley in between each jump. Be carefull if you crash or fall you loose all of your points. I've sucessfully gotten over 1,000,000 points this way.
Fresh Treds
Head to the in-game cheats menu and type in "newtreds" (minus the quotes) for some fresh treds on your vehicle.