A woman drinking a slurpee from 7-11. Photo Credit Charley Gallay/Getty Images Entertainment/Getty Images. On a hot summer day, a Seven Eleven Slurpee can hit the spot. However, depending on the size, the calories and sugar can add up quickly. The nutritional information for a Slurpee is based on an 8-ounce, or 1-cup, serving. The caloric content of a Seven Eleven Slurpee depends on the flavor. The majority of the flavors contain around 65 calories per serving. A Coca-Cola Classic Slurpee contains 65 calories, a Fanta Wild Cherry Slurpee contains 66 calories, a Mountain Dew Slurpee contains 60 calories and a Fanta Grape Slurpee contains 67 calories.