Is there any special kind of advice that can be given to such people? I think the answer is nope, the advice to be given is just a general statement which you tell them not to continue with the habit and also share more light on the consequences of what those habits can lead to. You can only talk but can not force the person to stop because who has ears should listen, perhaps you didn't ask them to get addicted. If you want to take it upon yourself to make them change, you should be ready to spend your money too paying a psychologist.