Most new models of hydration packs don’t come equipped with a reservoir that’s designed with an interior sleeve that can hold a bladder. If you need to bring a lot of water along on your next outdoor adventure, then purchase a dedicated hydration backpack or daypack, both of which will allow you to bring along as much water as you need. The difference between a regular backpack and a hydration pack is the dedicated space that secures and protects the bladder.