Preheat the oven to 180C, 160C fan, gas 4.
Mix the eggs, oil, water and the Betty Crocker Devil's Food Cake Mix gently together, and whisk (by hand or electric mixer) for 2-3 minutes, until smooth and creamy.
Pour the cake mixture evenly into the cupcake cases.
Bake in the centre of the oven for 18-20 minutes or until a rounded knife inserted into the centre of the cupcake comes out clean, then cool on a wire rack.
Place a pot each of vanilla into 2 separate bowls and the remaining ½ pot into a third bowl. Colour one of the larger bowls with the blue colouring, one with the pink colouring and leave the smaller bowl as it is. Spoon the blue and pink icings into separate piping bags with a round nozzle. Place the plain vanilla icing into a piping bag with a star nozzle.
Heat the cream in a pan until almost boiling. Place the chocolate into a bowl and pour the cream over the top. Stir until melted then let cool to almost room temperature.
Pipe half of the cupcakes with the blue icing and half with the pink. Drizzle over a little of the chocolate ganache then pipe a dot of vanilla icing onto the top and finish with a cocktail cherry. Add in the striped straw and voila you have your super duper Retro Ice cream sundae cupcake.