KOOL is a brand of menthol-flavored cigarettes sold in packs of 20.
Richard B. Riddick told Jack, that he gave a doctor 20 menthol KOOLs to preform the eyeshine surgery.[1]
They are shown in the comic-like release of Pitch Black: Slam City, where he is shown putting them into the pocket of the doctor as a "down payment". They may also be seen in Butcher Bay Correctional Facility when collecting the cigarette packs.