In a bowl, mix together a quarter cup of Dr. Pepper, one cup of cold milk, and a box of vanilla instant pudding mix. Whisk until well combined and then chill the mixture.
Once the Dr. Pepper pudding mixture has set, gently fold it into the whipped topping until fully combined.
Prepare your pie shell and pour the combined mixture into it.
If you're using maraschino cherries, drain them and place them on a paper towel to absorb any excess liquid before arranging them on top of the pie.
Freeze the pie for at least one hour, or refrigerate it if you're short on time.
