Calpis is a lactic acid bacteria drink that has been sold in Japan since 1919. It is a cloudy white liquid, diluted 4 to 5 times with water and drunk. The taste is cool and sweet.
The secret to its popularity is the abundance of arrangements. If you mix undiluted calpis with milk, it becomes like a mild yogurt drink. If mixed with lemon juice, it becomes a lassi-like drink.
When I was a child, my mother made calpis by diluting it even more than 5 times. Since children drink it a lot, parents usually give them a more diluted calpis to save up. When I grew up, I bought my own calpis and diluted it in the right proportions. It tasted strong. I felt so superior/proud that I had become an adult.
Calpis is sold worldwide. On a hot day, try mixing calpis with soda and drinking it in a glass with plenty of ice. And on a cold day, try mixing it with hot water and drink it as hot calpis. It will surely put your mind at ease.