In the Darkmoon Races, the “sack powerups” are supposed to provide you with “Racing Regs” reagents. However, picking up the sack powerups don’t currently yield any Racing Regs, making it impossible to use any Darkmoon Racer abilities that require the Racing Regs items.
I can confirm this to be the case for the Wanderluster vehicle. The ability Danger Zone can’t be used because there’s no Racing Regs items.