I worked at a theater in like 98-99, and we LOVED to bust people sneaking in. It was almost always kids, and just felt great to be like "That mother fucker is going to try some shit..." and be proven right. My favorite go to was when kids bought tickets to some movie, when it was clear they were really all there to see Southpark or Species or something. They would all go into the movie they bought tickets for, and then I would stand like 1 inch behind the door to the movie I assumed they were planning on sneaking in. Sure enough, a few minutes later the door would be thrown open as they all tried to shuffle in, looking over their shoulders to make sure no one saw them - only to end up face to face with me. Was fucking hilarious every time.
We also used to tell anyone with a big bag or backpack that we had to check it, and when it had candy and soda we would be like "Ok, you can give us all this and still see your movie, or you can leave but we aren't refunding your money." and 9 times out of 10 they would hand over all their shit. Keep in mine I was a 19 year old assistant manager working with a bunch of 16-20 year olds. Cinemark fucking gangsters lol.