No! As we like to say at Happy Gut, the sugar isn’t for you, it’s for the grains. Without sugar, water kefir cannot ferment. Sucrose is most easy to digest by the yeasts; they consume the sugar and put out CO2 (carbon dioxide, i.e. the bubbles in your water kefir) and ethanol. Then, as part of the symbiosis, the bacteria consume the ethanol and express the trace vitamins and minerals.
If you leave your ferment longer, for 48-72 hours, sugar levels in water kefir may be even lower. People with diabetes and others with low sugar tolerance have had luck with this method. However, if you add too little sugar, you are inhibiting the brew’s normal healthy development.