Does anyone make their own water kefir? Why do I keep getting that sick smell?

[MirandaGoshawk]

I've had a few batches that are fizzy and delicious, but not many. I change the sugar water every three or four days - any sooner and it just tastes like sugar water and any longer and it starts to smell. Dd says that when she was doing it she'd change the sugar water every day! I've bought a couple of new lots of grains (organic) this year and after a few weeks they smell disgusting. I use organic sugar and rinse the jar, funnel etc in very hot water. I bottle it & let it brew for a couple of days before drinking/putting in fridge. It's kept in the kitchen. Any ideas pls? TIA