A CNK challenge in Crash Nitro Kart means the player must collect the letters C, N & K and come in first place to win a CNK Token of a specific color. Once all CNK tokens of one color have been collected, the player can enter the corresponding gem cup. For example, collecting all red CNK tokens unlocks the Red Gem Cup.
Out of Time
The Purple CNK tokens are obtained in a different way. The player must enter the battle arenas; Temple Turmoil, Frozen Frenzy, Desert Storm, and Magnetic Mayhem to obtain the crystals in the arena before the time runs out. If the player is successful, he/she will obtain a purple CNK token. Winning this cup unlocks Zam.