Jack's defining character trait is that he's a "recovering" drug and alcohol addict. He appears high in flashbacks, and in one of those, a bong is seen in a background. He mentions having a cocktail of drugs including mushrooms, heroin, cocaine, LSD and pot, with the resultant trip inspiring one of his more ridiculous casino ideas. Later in a dramatic scene, he relapses, with a bong and bottles of alcohol clearly visible, in addition to cocaine on a table. Before leaving the suite, he snorts a line.
At the end of the film, he smokes a joint.