Easy win:
When racing in the speedways, if you get into third place, you can no longer flame or rocket the last two competitors or your position will stay the same. Instead, find as many warp stars as you can, stay with the red dots, and complete the challenge.

Unlimited lives:
Press Left, Right, Left, Right(3), Up, Down, B at the "Press Start" screen. A chime will sound to confirm correct code entry.

Go Through Closed Gates
You all know how annoying it is that you can't get past those two gates without the right type of breath, but I accidently found out how to get past them without the right type of breath, all you have to do is hold down the B button while on one part of the gate (If you bounce back that's a good sign that you're in the wrong spot). I hope you enjoy this cheat, the only benefit it gives you is more treasure. Or if you don't want to do this spend time finding the correct breath.

Gem Finder
Defeat Ripto then press LEFT and RIGHT until you hear a click. When Sparkster is near a gem he will point to it.