Get them addicted to something BETTER that isn't bad for them. And it doesn't have to be a drug, food, etc. It could be an activity (skydiving, mountain biking, something that gets the adrenaline going), or traveling somewhere really exotic that will blow their senses away. Again, you're looking for something that will give them a "high" to REPLACE the high that crack gives them. It's not the crack a person's addicted to, it's the high that it gives the nervous system.