A nice little plastic canteen. If your water bottle fantasies do not call for a standard 1 liter (or quart) canteen, consider this option. A smallmouth means easier drinking on the move, small volume means less weight to carry on your belt.

There was a time when a soldier had to do with a small water bottle, and everything else was a weakness of the mind. There was an upside to all this; the water bottles were physically smaller and thus fit better to various pockets and pouches, almost like a hip flask. Maybe one could have a larger reservoir in the rucksack and carry this on the belt - if you're not into bladders, that is! Of course, during winter a bottle does not freeze as easily as a bladder tube, hint hint.

Belt clip on the backside and a metal ball chain to keep the cap safe.

Used, maybe washed

These have been used and then sold off to the civilian market. All or at least some have probably been washed, maybe. As you probably guessed, wash before use - no machine washing! These are all in good serviceable condition for years to come - it's made so well that you could build a house with it, and then get into legal trouble after manhandling a burglar with it, but at least your bottle is still intact.