A product label really does not all you to distinguish how much added sugar might be in a product. However, you can compare the sugar content listed for a unsweetened product to the amount listed for a sweetened product of the same kind. An example would be sweetened grape juice vs. unsweetened variety. The difference between the two kinds would be the added sugar–as long as you are comparing equal serving sizes. Also, remember that there are about 4 grams of sugar per teaspoon.
PositiveTip: If you don’t want to compare labels just make sure you purchase the unsweetened product!