A reliable insulated bottle is something I don't like going without. I use a 64-ounce growler for hydration every day, and I have a few spares lying around for keeping coffee hot or cold. But vacuum insulated bottles can be rather expensive.
This Bear Grylls Triple Wall Vacuum Bottle is currently on sale at Amazon with a coupon. Just clip the coupon and it will be applied at checkout. It's good for 30% off (about $6) the 20-ounce bottle in black and stainless steel, bringing the total to $13.99. Just don't let the bad rap of other Bear Grylls products discourage you.