I don't include a hydration sleeve as a standard feature for a couple of reasons. First, as most my packs are for mountaineering & technical climbing, my customers tend to use bottles with OR insulated cases or thermos. 2nd, they add weight and provide a place for water to enter the pack.
That said, some of you like the option of using a bladder when it's not winter. the sleeve will hold a 3 L bladder, hose port exits above the lifter straps, the red panel in the photo below.