I don’t know where you are in the world but you certainly don’t need cigarettes or alcohol to have fun. Find friends who enjoy going to the coffee shops, food trips and if time allows, nature (as in hiking or resorts). In my experience, the first two don’t allow alcohol and cigarettes so you’re most likely be able to find people who don’t smoke and drink.
Also, find more health conscious people. They typically don’t drink and smoke as well. Depending on where you are, activities that takes place in doors and around families also don’t allow those substances. So inviting friends to something like a bowling or cinema works.
You just got to research the hang out spots for health minded people ans/or family friendly ones.
Don’t go to bars. Those are definitely a space where alcoholics gather.
I never drank and smoked in my life (nearing 30s now), and I can relate how hard it is to avoid gatherings that doesn’t outright requires alcohol and smokes.
You just got to be more diligent with picking your social circles. My friends are smaller, but at least I know they won’t pressure me to drink and smoke.
Some more ideas: Libraries, book clubs, alcohol-fre bars, gaming, art clubs, etc. find ones that align with your hobbies :)
Their question seems to be being able to socialize. Hence, the suggestions. So apologies for any misunderstanding.
That said, if the issue, is peer pressure, then my suggestion in choosing and limiting social circles still stands.
If none of their friends drink or smoke, they won’t have to worry about accidental peer pressure.