There have been experiments in which scientists have discovered that it is possible to predict the choice that somebody is going to make before they become conscious that they have actually made the choice. I will provide a link about this later, once I find it.

The drug addiction thing is simple. The chemicals in their brain which lead to the determinism to give up drugs becomes stronger than the desire to take them. If you're perhaps hinting intervention from God or the Holy Spirit, this STILL has nothing to do with free will because the decision to give up drugs is STILL determined by chemicals in the brain.

God = euphoric rush of brain chemicals = increased confidence and determinism = wanting to start afresh = decision to give up drugs

No... no free will there.