If you believe there has been a heatstroke, you would call 911 immediately. You then should move the person out of the heat, remove excess clothing, and cool the person in any way possible, such as a cool bath or shower.
Say no whenever you are offer alcohol, drugs, or tobacco.
Even when pressured a simply excuse is a better idea than ruining your life. You see many homeless people that still buy tobacco, drugs, or alcohol and no wonder they are homeless every dollar they get is spent on harmful substances. People use these products to wipe there worries away and do not think about the consequences of tomorrow.