Neither of these is technically a hydration pack, but it's easy to retrofit either one with a CamelBak StoAway ($35; www.camelbak.com), which is designed to slip into most any pack and provide the carrier with 70 ounces of liquid. Both the above Gregory and Kelty packs are equipped with hydration bladder sleeves and "feed" tube openings in the straps.
I can't imagine that a warm sleeping bag is in order. REI's Travel Sack +55 ($59; www.rei.com) should be just finea light synthetic bag with just enough insulation to keep you from getting chilled in warmer climates. A Cocoon Silk Mummy Liner ($49) offers a little extra warmth if it's needed, serves as a standalone blanket on very warm nights, and keeps the bag cleaner when used with a sleeping bag.
Hope that helps keep your guy on the go and comfortable as he's communing with the wonderful critters and plants of the Amazon!
For more expert reviews of a range of haulers, check out Outside Online's Backpacks Buying Guide.