I just kind of scanned the other posts, so sorry if this suggestion had already been posted.
I think you can buy these at wal-mart, but there are backpacks that have like a water bladder already in them. They come with a long hose that connects to the bladder, and then maybe snaps to your shirt? I'm not sure about that, but anyway, you're able to drink with out having to stop, fidget with zippers and such.
I think I'd get one if ever I'd take a longer ride.