Every theater around me allows it. I walk in with my bag of chips and vitamin water/vodka mix. Nobody says shit unless I'm already plastered and caused a scene <_<... like when I went to see Deadpool 2 on my birthday and was shitfaced > _>
I bring food in my bag to my local cinema but I always buy something cheap like small popcorn so that they don't suspect amything (there have been instances of people getting kicked out because they brought their own food)
Or.... baby formula.