They do a cheek swab as a drug test at the location I worked. All you have to do is be clean for 24 hours and you will pass. If your stupid enough to tell them you use then you obviously won't pass. Regardless of what they ask you, it's mostly to see if you have any prior experience and whether or not you possess the intellect to do the tasks they want you to do, which if your pushing carts or bagging groceries it really won't matter what you tell them unless your a complete walnut and make it clear your the type of person who enjoys setting things on fire, stealing change, or eating ink pens.
After the interview, but as part of the hiring process, they have you sit down at a kiosk and spend the rest of the day watching boring safety and procedure videos.