Puree the grape juice, grapes, kale, bananas, apple, and salt in a blender until smooth.
Pour the mixture through a fine-mesh strainer, pressing with a spatula to remove as much liquid as possible. Pour the mixture into 10 3-ounce or 8 4-ounce ice-pop molds, dividing evenly. Insert ice-pop sticks and freeze until firm, at least 4 hours and up to 4 days. Note: Think of this ice pop as a frozen green juice. It’s refreshing and tart, and it’s packed with good-for-you greens.