Yes. Water kefir grains have evolved to feed on granulated white sugar and cannot properly ferment without it. Thick sugars like turbinado, sugar in the raw, and brown sugar are too difficult for the Water Kefir grains to break down and process. Also, always avoid alternative sugars like honey, stevia, etc. as the culture will struggle to thrive.
For more information on sugars and their effect on your fermentation, read our handy sugar guide.