Unsweetened Grapefruit Juice

A few months ago, on a whim, I bought a case of unsweetened grapefruit juice. It's really really good... after I have added about 4 teaspoons of sugar to it. I am sort of hoping that I can downgrade the level of sweetener I need to add to it until I am drinking it without sweetener. I really need to add more juice, fruits and vegetables to my diet, but I also need to cut back on the sweeteners while I'm at it.