Pour 1/4 cup cranberry juice into a shallow bowl. Pour 3 tbsp. sugar onto a plate. Dip rims of 4 to 6 widemouthed glasses (6 to 8 oz., suitable for margaritas) into juice, then sugar. Set glasses aside.
Reserve 12 cranberries. In a blender, whirl the remaining cranberries, cranberry juice, and sugar, the lime juice, tequila, orange liqueur, and ice until smooth and slushy. If necessary, blend in 2 batches, then mix together. Divide among glasses and garnish with reserved berries, skewered on toothpicks.
Note: Nutritional analysis is per serving.