Well, I suppose if it was me fantasising about alcohol or one of my other addictions (as someone from the alcoholic side of the forum) I would be advised by my sponsor to do one of 2 things...
1 - cut the fantasy short by re-creating my step 1 inventory (the list of how alcohol makes my life unmanageable when I succumb to it)
2 - play the tape forward. Instead of staying in the comfortable lovely part of the fantasy, carry straight on with it to what would happen next, and next, and next, n based on previous experience.
Remember how horrible it was. All the horribleness. Every bit of it. Don't buy that fantasy.