We usually carry 3-4 of these Playpus 2-liter bladders. Most of the time they're empty (and light! and compact!). But they when you need them they're there to haul water. We can camp the night, fix dinner and breakfast, and start riding the next morning with about 6 liters of water, although that's pretty tight. When we know we're going to have a "dry camp" at night, we load up with water so we can do it.

We've also ordered a new item from Ortlieb: A 10-liter water bag (with shower fitting!). We'll use it for unfiltered water. It can be used to haul water before it's filtered with our Pur.
(Katadin) Hiker water filter.