Yes, you are absolutely allowed to bring a Hydroflask or any reusable metal or plastic water bottle into Disneyland. In 2026, the resort's policy encourages hydration, especially given the intense California sun. Unlike at an airport, your bottle does not need to be empty when you pass through security; it can be full of water, juice, or other non-alcoholic liquids. However, glass containers are strictly prohibited (with the exception of small baby food jars) for safety reasons. To make the security process faster, it is helpful to take your Hydroflask out of your bag when passing through the scanners, as the dense metal can sometimes trigger an additional manual check. Once inside the park, you can refill your bottle for free at various hydration stations or ask for a complimentary cup of ice water at any quick-service dining location.