Heat and humidity are as much a part of a Japanese summer as festivals and fireworks. With the threat of dehydration always looming, it’s a smart idea to always carry a cool, rehydrating beverage with you, but if you’re sweating profusely, you can bet the plastic bottle your drink is in is doing likewise.
To keep the rest of the contents of your bag from getting damp, you could wrap the bottle in a hand towel. A more effective alternative, though, is to slip a specially designed cover over it, and if you’re going that route, why not use one of these cool Sailor Moon costume covers that you can get for free with a bottle of Japanese tea at Mini Stop convenience stores?