Dissolve 1/4 cup sugar in the water and add the kefir grains. I like to use a one-quart mason jar for making water kefir.
Cover with a thin towel or cloth and rubberband. Let sit for 24 - 48 hours or until it bubbles when you move it.
Strain out the kefir grains.
Depending on how much lemon flavor you like (I like a lot) squeeze in fresh lemon juice from a whole lemon and the additional 2 teaspoons sugar. Allow it to sit out for another 24-48 hours, either lightly covered (for non-fizzy) or use a two-part canning lid (for fizzy).
Chill completely and serve.
If you have city/tap water make sure to boil and cool or let it set out for 12 hours first to get rid of the chlorine.Also, note that nutritional values will be different than stated as the kefir culture will consume the sugar as it ferments.