I'm playing the devil's advocate, as I will probably disagree with the majority.
In my view, 100% fruit juice means just that: 100% fruit juice. Think of sour grapes or sour oranges turning into juice. Most people LOVE sugar and they probably wouldn't settle with sour grape juice, even it's a 100%. So what happens? The juice company may simply add sugar and still call it 100% fruit juice! They won't tell you it has added sugar. Mater of fact, I'm shocked when I read fruit juice nutrition labels. Most juices are loaded with sugar. Yesterday, in a local food store, I found one with 39 grams of sugar in one liter. I might as well eat a lump of sugar...
Whole fruit juice, on the other hand, implies there's no added water, sugar, or preservatives:
https://www.amazon.com/UpGrape-100-Whole-Grape-Juice/dp/B017...Which basically coincides with the definition of "suco integral": "Suco integral é o suco da fruta puro, sem adição de açúcares, e na sua concentração natural..."
http://www.cultivando.com.br/o-que-e-suco-integral/