I don’t do dairy (intolerant) but a French friend gave me ‘graines de kefir’ for the water type.
Very easy to manage but yes, it is a little like sourdough starter (levain); one must reset the culture each few days.
The good news is that any extra liquid or grains can be poured down your toilet; if you are on a septic tank, the lactobacillus bacteria are the same family as the ones that plumbers recommend you feed your tank with to encourage ‘activity’. So it works well inside us and outside.
In summer it is particular nice to make a naturally fizzy lemonade (or any flavour you want to add); you just drain the liquid into a sealable bottle, I used the swing stopper type, add a teaspoon of sugar to feed the remaining lactobacillus and your flavour. Two to three weeks later it’ll really blow with the carbon dioxide in it! Refreshing. Truly like store bought.