Tart cherry juice can help with: 1) sleep due to the melatonin they contain, 2) pain and soreness by fighting inflammation, and 3) aging due to the antioxidants they contain which fight free radical damage in the body.
One ounce of tart cherry juice concentrate has the equivalent sleep benefits of eating 100 fresh cherries. It has about 80 calories per serving, so it's a small amount of sugar. Generally, I recommend against fruit juice for people who struggle with weight or food addiction. Frozen cherries or whole ones may be good alternatives for some people.