The Deuter Streamer and Source Tactical both have a slim profile that makes it harder to flip inside out (but not impossible). We certainly give kudos to CamelBak for trying to do something different, but we’re not sure that the Fusion’s zipper has any merit over a more secure slider—and it seems to have a lot more potential to fail over time. Conversely, twist-tops are imprecise and often have places where water can hide, which isn’t helpful when you’re trying to dry the reservoir out completely. One of its standout features is the wide tube and high-flow bite valve, which combine to deliver a heavy stream of water at each sip (we find the Crux really fun to drink out of because of this). And if your hydration bladder doesn’t come with one, it’s often possible to add the customization with components like HydraPak’s Inline Connector or Osprey's Quick Connect Kit.

HydraPak’s new Contour here is our favorite design for minimalists, with fewer features and significantly less bulk and weight. We prefer the latter, as it allows you easy access rather than having to rifle around at the base of your pack. Whether you’re adventuring in the cold (or extreme heat) or want a durable hydration bladder that can take a beating, the HydraSleeve is one tough cookie. In general, reservoirs with sliders are the easier of the two to clean and dry—the openings are wide enough to fit your whole arm in, and some offerings from HydraPak can even be turned inside out and placed in a dishwasher.