I'm not sure what the "official" policy is, but I know they are very lax about enforcing it. Many people bring in food and drinks. I have brought in cans of soda (and even a beer!) and bags of chips and they always looks the other way.
I think if you brought in a big cooler, they might care, but otherwise, they're pretty lenient.
The only people who check are supposed to be checking for guns and bombs and not food! (I think?)
JULIE