What do these tokens do?

I was playing Diddy Kong Racing DS, and noticed these coins:

I happened to pick one up, but I have no idea what they are for, much less how to use it.

What can I do with this coin? It seems like I can only have one at a time.

Solution 1:

The coins with an up arrow on them are upgrade coins.

These coins are activated by pressing 'X' and will upgrade any weapon or item you are currently equipped with. Weapon and items are found through the numerous balloons scattered throughout the course.

Upgrades are as follows:

Red Balloons: Missile Shield

Blue Balloons: Autopilot

Green Balloons: Rare Coins

Yellow Balloons: Invisibility

Rainbow Balloons: Radio Missle