That's right, the body needs sugar to run properly, specifically the only energy source the brain can consume is glucose (sugar in its simplest form), like the sugars found in fruits. Unless it's a highly sweetened fruit juice drink, full of unnecessary syrups or the like, the benefits faaaaar outweigh the amount of sugar in fruit juice. But if it still worries you, you can always switch to juices that say "NOT from concentrate" right on them, they are lower in sugar naturally unless they are sweetened. Then there's vegetable juice, though the nutrients are completely different in fruits from those in vegetables. Remember you need both to be healthy!
Or just eat some fruit. That's what I like to do