For years I've been using the one liter bottles that Schweppes tonic water and club soda comes in. They are narrower and taller than the Gatoraid bottles and are designed to contain pressure so they are quite sturdy; I've never had one fail. They weigh a bit over an ounce. I also use the half liter Aquafina bottles when I'm hiking in well-watered country. They weigh about 0.8 oz each. Like OM, I have been known to loose caps for these bottles. If it is critical, I take an extra cap along: they only weigh a couple of grams.