Serious answer: to the countryside, away from the city and its lures, away from the dealers and with a bit of luck also away from the legal dealers of alcohol, even though that would be harder to achieve.
It seems to me it would be cheaper to give the committed substance abuser their drug of choice for free in a safe, separated and controlled setting, rather than maintain this magical thinking that one day they will turn things around on their own in spite of overwhelming evidence to the contrary.
Cheaper money-wise, maybe. Probably if and when the supply of those drugs has been taken out of criminal hands - something which is long overdue as the 'war on drugs' does nothing but guarantee high prices for criminals while it does next to nothing at all to limit the amount of drugs on the market. As to whether the 'move to the country' scenario works depends on the reason for the addiction. For some it probably will, others will either keep their addiction or change it for another one.
It will improve the quality of life for the addicts as well as the city climate, as to whether this is worth the extra costs compared to a state-supplied drug stash is up to society to decide.
I was thinking move them to the country AND supply them with their drug of choice, at least until hopefully someone discovers a miracle cure for addictive behaviour, which would be a better solution. Or why not relocate them to a closed environment with no abusable substances whatsoever?
Some people are incapable of looking after themselves, or fall into addiction after horrible experiences, and leaving these people to stew in their own juices rather than intervene is inhumane. We do after all section people that are a risk to themselves or others, so this is not without precedent.
Then try to find a way to live a life which does not solely revolve around getting the next hit. This will work for some, it won't for others. An alcoholic will find it hard to quit drinking while living in a pub so getting her out of that place is one way to give her a hand in breaking the addiction.