Camelbak has a lightweight insulated bike bottle that keeps things cool four times longer. The outer surface is lined with aerogel, and the bottle itself is BPA-free plastic. I like just about everything about the Camelbak Podium Chill bottle. First, it doesn't weigh any more than a non-insulated bottle and it is the same size as most, with a 21-ounce capacity. It fits into bottle holder on a bike, in a waistpack, or your car cup holder.
My walking buddies discoveryed this bottle and soon I saw them everywhere. You just sip the water through the straw, eliminating the need to tilt the bottle up to take a drink. That means you don't block your own view, which is a good thing to avoid when walking. If you are aiming to drink a specific amount of water, you'll appreciate the marking on the side which tell you how much water is left. Original Camelbak Better Bottles were made of polycarbonate, but now they are made of BPA-free materials.
Stainless steel is BPA-free and doesn't need to be lined with polymers that might contain BPA or other substances of concern. Klean Kanteen promises that the highly polished interior surface is non-leaching and toxin-free. But I can still detect a metallic taste in the water when it sits for any amount of time. Stainless steel bottles transfer heat and cold faster than plastic, so your drinks will reach room temperature faster.
SIGG specializes in aluminum bottles lined with a resin to protect you from off-tastes in the water and any stray aluminum molecules. Before the plastic fears, there were fears about aluminum. SIGG bottles were rated as the toughest water bottle in a 2006 Backpacker magazine test. The mouthpiece has a "mud-cap" and you depress it to drink or twist it to seal it off. One drawback of metal bottles is that you can't squeeze them to improve the water flow, which some users find to be a flaw. Aluminum is very lightweight. But it is also prone to quickly heating up or cooling down and sweating in humid climates. SIGG now has wide-mouth models, which I prefer as I can add ice cubes to the water.
8. ALEX Bottle
The ALEX bottle is a modular stainless steel bottle that comes apart for easy cleaning by hand or in the dishwasher. This kills two concerns -- icky bacterial/fungal growth and concerns over plastics. I didn't find any off-tastes in water left in it overnight. The ALEX bottle is wider than most due to the central flange, and may not fit into your existing bottle carrier. You must remove the top cap to drink from it.