Any wine that is fully fermented (meaning the yeast eats all the sugar) will be sugar-free.
Wine is made by adding yeast to grape juice. Then, the yeast eats the sugar, producing alcohol and carbon dioxide as byproducts.
In a full fermentation, the yeast eats all the sugar and dies. Modern, industrial winemakers use sulfur dioxide ("sulfites") to kill the yeast early, which leaves residual sugar in the wine. And, some even add sugar back into the wine. This achieves a sweeter palate to appeal to the American market.
By contrast, natural winemakers let native yeasts consume as much as sugar as natural, and then the yeast dies.
We lab test every bottle for sugar so none of our bottles measure beyond 1g / L of sugar. Since wine doesn't have nutrient labels, lab-testing gives us the certainty to avoid consuming sugar.
We avoid eating sugar and recommend you do too!