Cinemark movie app gives free rewards
It seemed odd that they would be able to tell that you were actually at the movie. So I tried to put the app in Cinemode before going to bed, and woke up the next morning, turned it off and got a reward. So apparently it doesn't know that you're actually at the theatres or not.
So far the rewards I collected are - free medium fountain (first time user) and Free small popcorn with purchase of any size fountain. The good thing about these coupons are that you can upgrade to a larger beverage or popcorn and they'll apply the credit for the coupon towards the price.