Set 1 oven rack on the highest level, then preheat broiler.
Using a small serrated knife, cut around grapefruit to separate the fruit from the skin and the segments from each other (just like your mother did for you). Pour out a bit of the grapefruit juice to make room for the vodka.
Drizzle 1 ounce of vodka over each grapefruit half and let it seep between the slices (I doubt your mother did this for you).
Immediately before broiling, sprinkle 1 1/2 teaspoons of sugar over the top of each grapefruit half.
Place grapefruit directly on rack under the broiler and broil for 3 minutes. Garnish with a raspberry or strawberry, if available. Serve immediately.