Hi, Daniel!
You are welcome to bring
food and beverages into any of the theme parks. There are
a few rules: No bottles or alcohol, and only small, soft sided coolers (no coolers on wheels). Items cannot be heated or cooked in the restaurants, so do not bring anything that needs heating.
I like to toss a water bottle and a few snacks in my backpack. However, remember that cups of ice water are free at any counter service location if you prefer to just grab a quick water as needed rather than carry around heavy water bottles all day long.
If you do not want to carry around your snacks or your jackets and tote bags, there are
lockers available at the entrance of each park. I find the lockers helpful if my family is planning a super long day in the parks.
Wishing you magical days at Walt Disney World!
Cathy