The use of water-soluble plant-based extracts is a viable option of a non-dairy substrate in developing new food products, such as for kefir fermented beverage. The aim of this study was to develop a vegan fermented beverage with water kefir in the water-soluble coconut extract (WSCE), with inulin. A factorial design 23 was applied, with independent variables: coconut sugar (2.0; 6.0 and 10.0% w/v); inulin (2.0, 2.5 and 3.0% w/v) and xanthan gum (0.0; 0.13 and 0.26% w/v) and dependent variables: growth of kefir grains, fermented beverage yield and lactic acid. The growth of kefir grains was higher when the concentrations of inulin were close to 2.8 and 3.0% (w/v) and xanthan gum up to 0.26% (w/v), influencing in 90% the rate growth. Fermented beverage yield and lactic acid were between 80 to 82.5% and 1.2–1.25%, respectively, when of xanthan gum and coconut sugar were between 0.26 and 10.0% (w/v). Still, fermentative process was significant in terms of nutritional and enzymatic contents. The water kefir showed great potential for adaptation to WSCE in 24 h of fermentation, favoring the development of a non-dairy fermented beverage that may prove to be an alternative for lactose intolerant, allergic and vegans. Display omitted •Water kefir favored the development of a non-dairy fermented beverage.•Water kefir has adapted well to the coconut extract in 24 h of fermentation.•Inulin increased in the viscosity and had meaningful interaction on growth of kefir.•Inulin and coconut sugar are viable matrix for the upkeep of kefir microorganisms.•Fermentative process was significant in terms of nutritional and enzymatic contents.