One cup of unsweetened pineapple juice has 25 mg of Vitamin C, which is 1/3 of the daily amount for women, and a little over 25% for men. It also contains about 95 grams of carbohydrates, 1000 grams of potassium, and 75 grams of magnesium. So pull up a chair and a tall glass of pineapple juice. These are the 9 pineapple juice benefits you'll want to know.