Hydration packs are portable water storage systems designed for outdoor activities like hiking, biking, and running. They typically consist of a lightweight backpack with a built-in water reservoir, or bladder, and a tube for easy sipping. This design allows users to stay hydrated without needing to stop and reach for a water bottle. These packs come in various sizes and styles, catering to different activities and durations. Many hydration packs also feature additional compartments for carrying essentials like snacks, tools, or first-aid supplies, making them a convenient choice for adventurers who want to travel light while staying hydrated.