Alcohol and marijuana is the most common combination of substances people use to get cross-faded.
However, alcohol is one of the most commonly used substances overall, in part because it is socially accepted and legal for anyone old enough to purchase it.
Because so many people drink alcohol, they will use almost any other type of substance to amplify the feelings of drinking. This includes legal prescription medications such opioids, Adderall, and Xanax, to illegal ones like cocaine and heroin.