The standard Japanese beverage can size is 330 ml (almost the same as the US), for a couple of years now manufactures have been selling 135 ml cans. It's kind of convenient, especially is you are not that thirsty.
Above are three cans of Asahi Super Dry, 135 ml. These made it to the summit of Fuji!
Coca Cola also sells drinks in little cans. In Japan, Coca Cola is made with Sugar, just like Mexico. Like the can says, it's refreshing & uplifting.
This summer Pepsi sold Salty Watermelon, it's okay. Pepsi makes this drink using high-fructose corn syrup, not as good as soda's made with sugar.
Above is an old guy enjoying a 135 ml super dry during a festival in Nagoya. You can get an idea how small they are.