1. Thoroughly wash the grapes and pat them completely dry with a paper towel. 2. In a small bowl, stir together the Greek yogurt, lime juice, and honey or maple syrup (if using). 3. In a separate shallow dish, combine the crystallized lime or citric acid with the granulated sugar or monk fruit sweetener to create the sour coating. 4. Using a toothpick or fork, dip each grape into the yogurt mixture until fully coated. 5. Roll the yogurt-covered grape into the sour coating mixture until evenly dusted. 6. Place the grapes on a parchment-lined baking sheet in a single layer. 7. Freeze for at least 2 hours or until the yogurt is solid and the grapes are frozen.