I doubt they were on drugs. Considering how many takes they might have to do. I could imagine the actors have done the drug before and just used the experience.

actually being on drugs isn't something you can fake.
Where you on drugs when you wrote this? You must have been because you can't fake logic like that.

or maybe these actors and the creators have done and seen people on those drugs before so they were really good at mimicking it? highly doubt producers would let them get f'd up on the job. it's possible, but odds are against it.