Soften the cream cheese: Let the cream cheese sit at room temperature for about 30 minutes until soft.
Beat until smooth: In a large bowl, beat the cream cheese with an electric mixer until smooth and fluffy.
Add milk and soda: Pour in the sweetened condensed milk and Baja Blast soda. Mix until smooth and slightly bubbly.
Fold in whipped topping: Gently fold in the whipped topping. Add pudding mix if using and mix until thickened.
Assemble the pie: Pour the filling into the graham cracker crust and smooth the top.
Chill until set: Refrigerate for at least 4 hours or overnight until firm.
Garnish and serve: Top with whipped cream and lime zest. Slice and serve cold.