How do you mask cocaine?

You can't nessicarily mask cocaine. But, If you mean hide the smell of cocaine try coffee grounds and/or bar soap with a dominate smell, also a body (living or dead). If you mean mask cocaine in a drug screen, you are up-the-creek. Time is the only thing that will give you a passable drug screen, usually A gram for every 3-5 days (depending on metabalism of your body).