When we were preparing for our trip to the Grand Canyon, we were looking at several different water bottles/reservoirs.  We decided on the Camelbak Unbottle.  As shown below, it has a bite valve and is insulated.  The insulation worked really well at the Grand Canyon.  While the first sip was usually warm because it was in the uninsulated tube, the rest stayed quite cold all the way to the bottom.  We bought two 100 oz Unbottles from Campmor.com.

Camelbak 100 oz Unbottle