One of the beauties of a full 16-20 oz water (or soda) bottle, is the great grip that's possible. It just fits perfectly in one hand, and a strike hard enough to knock out an assailant won't rupture the bottle.
No need for uber-tactical battle-ready hydration carrier units. No freezing, slingshotting, or lead-filling required. Just the willingness to carry a full water bottle around.
Oh, yeah, you can drink it, too, if you bring several, or the threat of dehydration is more serious than the possibility of attack.