My water kefir smells unpleasant. What could be the reason for that?Updated a year ago

It is possible that your water kefir has cream yeast. 

Here's what you can do about it:

1. Use a metal lid (alternative: metal lid and band) that allows little or no air to pass through. Nevertheless, make sure you open the water kefir from time to time to release CO2 or use an airlock lid.
2. Add enough sugar!
3. If you ferment tea or coffee with water kefir cultures, boil them first.
4. Use enough liquid when making kombucha. In the case of kefir, you can also add a shot of successfully fermented water kefir. Lemon slices or lemon juice are also great.
5. Always rinse your fermentation utensils thoroughly. Just using warm water is not enough...