If a therapist gives an alcoholic a drink laced with a nausea-inducing drug so that she or he will become ill after drinking the alcohol, the therapist is using what?

The therapist is using Aversive conditioning or therapy.

Explanation:

Making use of a method involving the use of unpleasant things to stop unwanted or bad behavior is regarded as aversive conditioning.

In this case, the therapist is trying to stop the individual from consuming alcohol.