You can order a child's soda at counter service without ordering a child's meal. I got one yesterday for $1.00 plus tax.
Also, we take our bottle of water and ask for 2 cups of ice water at lunch and refill our bottle for later. Most of the time I just take several bottles of frozen water with us.
They have become very relaxed on bringing food into the parks recently. We always bring chips, crackers and cookies, and bananas for snacks. Two weeks ago I saw a family eating cut up melon from a tupperware container during the parade at MK.
Enjoy your trip!