There are a few go-to snacks that I like to bring to the parks with me when I know I'm going to be a while and I don't feel like spending money. Worth noting I am not sponsored by any of these brands, but this is legitimately what I like to bring when I go!
Same goes for bottles of water; they're about $3 in the parks, so it depends on what bag you're bringing, how long you're planning on spending in the parks, and your food budget if you bring it or just buy a whole case at the grocery store and pack some in your bag.
One thing I always bring in my bag if I know I'm going to get a Dole Whip or eating at one of the restaurants is a measuring cup! Thank goodness for the stackable and collapsable kinds you can buy now because they don't take up a lot of room in my bag. They're a serious lifesaver when it comes to staying on plan and allowing an indulgence without it feeling like an indulgence!