The following is from thewirecutter.com
The Best Hydration Packs for Day Hikers
After more than 50 hours researching and testing hydration packs, including hiking with them, torturing their components, and downing enough water to almost risk hyponatremia (yes, it’s possible to drink too much water), we’ve come up with our favorite hydration daypacks for moderate hikes…
Upgrade Pick: CamelBak Fourteener 24
The best men’s pack for all-day hikes: This large but comfortable daypack easily holds its 3-liter reservoir and all the gear you’ll need for an ambitious outing.
This pack easily lives up to its name; it’s plenty big and rugged enough for an all-day assault on one of Colorado’s famed 14,000-foot peaks. For men looking to carry multiple extra clothing layers, lunch, camera, and other odds and ends—in addition to plenty of water—the CamelBak Fourteener 24 hit the sweet spot in terms of capacity, useful features, and comfort. The pack’s 3-liter reservoir is one of the largest you can buy, and it’s easy to use. Our testers especially liked this pack’s semi-rigid back panel suspension system, which handled heavy loads with ease.
Budget Pick: CamelBak Arête 18
Great for travelers: Small enough to stuff into a suitcase, this pack contains a 1.5-liter reservoir, perfect for staying hydrated during days of sightseeing and light hiking.
For people who want a basic, lightweight hydration pack—one that’s affordable as well as perfect for traveling—we recommend the CamelBak Arête 18. Constructed with relatively thin nylon and minimal padding, this pack easily folds up to tuck into your luggage, yet it’s comfortable when carrying modest loads. Its 1.5-liter reservoir holds just enough water for a pleasant afternoon sightseeing in a foreign city or strolling along an easy trail.