The childhood favourite, all grown up — vodka, grenadine, and a maraschino cherry.
Most commercial grenadine (Rose's, for example) is corn syrup with red food colouring and artificial flavour — it has nothing to do with actual pomegranate. If you use it, the Dirty Shirley will be very sweet and one-dimensional.
Real grenadine (Liber & Co., Small Hand Foods, or homemade from pomegranate juice and sugar) has tartness, complexity, and genuine pomegranate flavour. The difference in the final drink is dramatic. It's worth seeking out.
Replace lemon-lime soda with peach soda or add ½ oz peach schnapps. Sweeter and more summery.
Add a splash of blueberry juice and use blueberry vodka. The colour goes deep purple — visually stunning.
Add 2 dashes of hot sauce (Cholula works well) or use a jalapeño-infused vodka. The heat against the sweet grenadine is genuinely surprising.
Blend all ingredients (minus soda) with ice. Pour into a glass, top with a splash of soda for fizz, and garnish as normal.