For the Rimming Sugar, mix sugar and vanilla on a small plate. Add food color; mix until sugar is evenly tinted. Wet rim of beverage glass with water. Dip rim of glass into black sugar to lightly coat.
For the Marshmallow Eyeballs, cut marshmallow crosswise in half. Place 1 drop food color in center of cut-side of each marshmallow half.
Fill cocktail shaker two-thirds full with ice. Add cream, simple syrup, vodka and vanilla; shake until well mixed and chilled. Strain into rimmed beverage glass. Top with club soda. Garnish with Marshmallow Eyeballs. Serve immediately.