They can be educated out of the need for requiring artificial stimulants. Life would be much more interesting, exciting and always evolving.
All drug addicts would be taken care of and provided with the necessary treatment to overcome their problems without the dependence on drugs, alcohol or tobacco; all without a price tag. Not using money would eliminate the sale of drugs, prostitution, etc.
In a society where people are brought up with access to information and resources, there would far less stress or need for these artificial substances.
Exercise, and better methods of understanding others and the world around them, will serve to relax people or bypass tensions overall. People would also learn how to express themselves without needing substances to say what they think.