The consumption of apple cider has decreased in Brazil due to its poor quality and competition with other sparkling beverages. Commercial and experimental ciders (varietal ciders) were evaluated for physicochemical and isotope of 13C analysis. The analysis showed differences between the products (p<0.05), separating the commercial and experimental samples using principal component analysis (PCA). The isotope of 13C analysis in commercial ciders was efficient to determinate that 20 to 80% of sugars content are coming from other sources, such as sugar cane. The cider "A" had the highest addition of sugar from other sources, however, it did not present the highest total sugar content and total solids, indicating that, in this cider was added water (dilution). In this way, the final alcoholic content, possibly, was corrected, which is not allowed in Brazilian legislation. The analytical and isotope of 13C comparison between varietal and commercial ciders were efficient to detect the added compounds and to identify the cider dilution that compromises its sensorial quality.