1 measuring/cooking teaspoon = 4 grams of sugar (as read on the nutrition labels).

Read the label on the container of juice. Find the number of grams of sugar. Divide by 4. That will give you the number of teaspoons of sugar in one serving.

Then take that number and multiply by the number of servings per container. That is how many teaspoons of sugar are in the coantiner. If you're lucky, that juice box will have one serving per container.

Now actually measure it out into a bowl or onto a paper plate.

This will give you a nice visual of how much sugar you or your child are drinking. If it's 100% juice, then obviously the sugar in it is sugar that's already found in the juice, nothing added.

If it's not 100% juice, then a certain portion (generally a very high percentage) of it is added sugar. Could be in the forms of HFCS, sugar, or if you want to drink the "organic bullshit pretend healthy" stuff, it could be evaporated cane juice, brown rice syrup, maple syrup, agave nectar, or honey.

(BTW all liquid forms of sugar are digested in the liver instead of the intestines, the same as HFCS.)

Of course, it's up to you how to interpret this. But I think people should be informed.