You can bring in pretty much anything you like except for alcohol. The food/drink in the zoo is pretty expensive, but keep in mind that those proceeds go toward the zoo's amazing conservation efforts. I usually bring sandwiches, snacks, and water in a backpack, then I purchase a $12 soda with unlimited refills ($6 sodas are $1 / refill, so the expensive one pays for itself) to share with my party, along with any incidental beers (starting at $7-$8), pretzels, or churros (about $4 ea).
We took in a cooler but we did but other stuff expensive but it goes to feeding the animals they do not take tips at the food places
there was no restrictions about food from outside the zoo. Actually it's better since the food inside much expensive. every time I took my home made sandwiches, juice, fruits and my coffee.
Thanks! Your answer is awaiting moderation.