Usually on backpacking trips I’ve carried a Nalgene bottle and a couple of hardier plastic 1/2 liter bottles (like you get at any gas station, but stiffer plastic). On longer trips I might use a 1.5 liter plastic bottle, too.
I recently did a day-hike and a short trip with a new gadget – it turns a regular water bottle (with a small mouth) into a hydration bladder, complete with bite-valve. I really liked it! I find I drink more water when it’s super convenient to do so. I can drink while using trekking poles in both hands. Love that! Unfortunately, DutchWareGear.com has stopped selling them. Hopefully someone else does – I haven’t checked Amazon, yet.