Add everything (except the pink grapefruit soda) to a Creami tub and stir to combine. Cover and transfer to the freezer for 24 hours, or until frozen through.
When ready to serve, pour in 100ml (3⅓fl oz/⅓ cup + 1 tbsp) pink grapefruit soda into the tub and churn on FULL, SLUSHIE in your Creami. If the slushie is too thick, add 3 tbsp more pink grapefruit