These Low Calorie Watermelon Vodka Cocktails are just 159 calories for a big drink, and so fun and refreshing! You can add more vodka if you like, but the idea behind these dinks is to be a light afternoon drink. Like a White Claw level alcohol. Special Tip: If you want your drink to be super slushy, cube and freeze your watermelon for a few hours and it will be more like a slushy.