CALPIS, it is produced by Asahi (a famous Japanese beverage company)
https://www.asahigroup-holdings.com/en/brand/calpis/
If you are Japanese, absolutely know it. I love this beverage.
It does require water. The brand recommends; liquid : water = 1 : 4 (5)
My favourite portion is 5 or 6 water. And using COLD water is a regular way to drink it. Normally, that is a summer drink.
In recent decades, the brand has also commercialised it as a hot drink in winter. I like both ways. So, I invented a new quick recipe for winter.
Do you have herbal teas, which is a berry type? That would fit wonderfully.
1. Make a cup of herbal tea in a regular way.
2. Pour the liquid little by little. (adjust to your favourite amount)
3. Sip it slowly
These 2 types were so good with the CALPIS as well!!