Over the years we have had ample opportunity to use a variety of hydration reservoirs from a variety of sources.  The unit that we keep coming back to is TFO's® BIG BORE TANKER.  We sell the two liter size (that's 68onces of H2O). 
 
In our humble opinion, TFO has the best bite valve on the market and comes equipped with an integrated on / off switch.  There are very few things that tick us off more than finding our drinking water sloshing around the bed of the truck after a 45 minute, low four-wheel drive crawl.  TFO's positive on / off valve keeps your water in the reservoir until you need it. 
 
And even after sitting in the truck for a few days, our water never tastes like plastic.