Hello there, Mike!
Welcome to planDisney and thanks for your question! I'm a huge believer in being prepared as much as possible when I'm traveling, so I think it's great that you're already considering what goes in your park bag to keep you hydrated.
The
Disneyland Resort Park Rules and Regulations do have some limitations around what you can bring into the parks, such as glass containers and backpacks larger than 24" long x 15" wide x 18" high. As long as your hydration pack isn't larger than the size limit you should be just fine! There are plenty of
water bottle filling stations across Disneyland Park and Disney California Adventure Park, so you'll always have a good option to refill your pack or water bottle. You don't want to be running on empty!
Speaking of being prepared, did you know that you're also welcome to bring your own snacks into the parks? I like to use disposable plastic containers to hold quick snacks like grapes, carrots, crackers, and granola bars so that my snacks don't get squashed in my bag. Once I've finished my grapes the empty container is the perfect way for me to carry home a favorite treat, like something sweet from
Jolly Holiday Bakery and Cafe!
Luck favors the prepared, Mike, and you are on your way to being totally prepared for your trip to the Disneyland Resort. If you have more questions I hope you'll
send me a note so I can help you out!
Keep moving forward!
Amanda