Need your suggestion

I 19 M and am completing my studies in city A and my childhood friend also 19 M lives in city B

I recently got to know(From himself) that he started smoking and drinking. I myself being an avoidant of any kind of intoxications was very shocked to see this and really want him to stop doing so, but even if I tell him to stop,I know he won't. I can't even tell his parents also as he would never talk to me again if I do so....

What should I do?