If you don't already do it, something I learned from some Japanese friends is to fold the towel around the (cold or frozen) water bottle in the hot days. It kee

If you don't already do it, something I learned from some Japanese friends is to fold the towel around the (cold or frozen) water bottle in the hot days. It keeps the bottle colder for longer, avoids condensation/wetting the insides, and now you have a damp fresh towel if you are sweating, which is nice.