1 (1.5 fluid ounce) jigger vodka
1 (1.5 fluid ounce) jigger cranberry juice
1 (1.5 fluid ounce) jigger grapefruit juice
2 (1.5 fluid ounce) jiggers sparkling water
1 lime wedge
Fill a cocktail shaker with ice; add vodka, cranberry juice, and grapefruit juice. Cover and shake until the outside of the shaker has frosted.
Pour sparkling water into a glass. Pour in vodka mixture. Garnish with a wedge of lime.