CNK challenge in means the player must collect the letters C, N & K and come in first place to win a Crash Nitro Kart 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.
remake, these have been changed to Nitro-Fueled CTR Challenges, likely due to it being marketed as a remake despite having Crash Team Racing Nitro Kart tracks.
The Red Gem Cup is unlocked by collecting the red CNK tokens in Inferno Island, Meteor Gorge,
Out of Time, and Assembly Lane. Winning this gem cup unlocks Dingodile.
Deep Sea Driving
Out of Time
The Green Gem Cup is unlocked by collecting the green CNK tokens in Jungle Boogie,
Barin Ruins, Clockwork Wumpa, and Android Alley. Winning this gem cup unlocks Zem.
The Blue Gem Cup is unlocked by collecting the blue CNK tokens in
Tiny Temple, Deep Sea Driving, Thunder Struck, and Electron Avenue. Winning this gem cup unlocks Polar.
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.