Welcome, Brandi, to the Disney Parks Moms Panel and thanks for your question!
You can most certainly bring Hydro Flasks or any other type of water bottle with you in to the parks at the Disneyland Resort. We really like our Hydro Flask because it keeps the water cold for such a long period of time! One thing to be aware of is the possibility of having to open your Hydro Flask when you go through
security as the bottles are opaque. We had to open ours occasionally just so the security personnel could take a quick peek inside.
You can refill your water bottles at any of the drinking fountains located throughout the parks, or you can ask for a cup of ice water at a
quick service dining location. Also, feel free to bring along any snacks you might want while you are at the Disneyland Resort. We usually fill our backpack with things like granola bars, apple slices, and crackers. Snacks and water are especially important if you are traveling with children. My daughter always seems to be thirsty or hungry immediately after we enter a queue for an attraction, so having munchies on hand is a necessity.
I hope you have a wonderful visit to the Happiest Place on Earth!
-Linda M.