pineapple juice is so sweet that often no sugar needs to be added. In fact, the only substance that is normally added to it is ascorbic acid, also known as vitamin C. This is added to protect color and flavor. If you prefer your juice without the extra vitamin boost, you can always juice the fruit yourself.
Be sure to avoid any pineapple drinks that are juice-like products and not actually juice. These drinks are just flavored sugar water and should be avoided.