Background: Diets rich in free sugars are associated with an increased risk of obesity. The aim of the present study is to estimate the intake of added sugars in the population of Spanish children and analyze the quality of the foods that contribute to this intake. Methods: An observational study was conducted to collect self-reported information on weekly food consumption in 1775 Spanish children (7–12 years). Nutrient contents were obtained from different databases. Two nutritional density indices were constructed taking into account all nutrients provided and compared with two previously described indices. Results: The average consumption of added sugars in Spanish children was 55.7 ± 1.0 g/day. The products that most contributed to added sugar intake were biscuits (13.3%), cocoa powder (11.1%), sweetened yogurts (9.9%), and dairy desserts (8.6%). Among these, dairy products had considerable nutritional value. Parents’ perception of nutritional value was not aligned with the actual nutritional value. Conclusion: The consumption of added sugars was higher than recommended. Public awareness efforts should focus on: (1) the reduction of consumption of low-nutritional quality products containing high amounts of added sugars; (2) the industrial reformulation of most consumed products to reduce sugar content and increase valuable nutrients; and (3) nutritional education.