In a small bowl, combine milk and orange cereal. Refrigerate for 2 hours or up to overnight. Let come to room temperature before using.

Preheat oven to 350°F (180°C). Spray a 13x9-inch baking dish with baking spray with flour.

In the bowl of a stand mixer fitted with the whisk attachment, beat sugar and eggs at medium-high speed until pale yellow and doubled in size. Beat in vanilla.

Strain cereal milk through a fine-mesh sieve, discarding solids.

In a medium bowl, whisk together flour, baking powder, pie spice, and salt. With mixer on low speed, gradually add flour mixture to sugar mixture alternately with ¾ cup (180 grams) cereal milk, beginning and ending with flour mixture, beating just until combined after each addition. Fold in finely crushed cereal. Pour batter into prepared pan.

Bake until a wooden pick inserted in center comes out clean, 25 to 30 minutes.

In another medium bowl, combine condensed milk, evaporated milk, and remaining 1 cup (240 grams) cereal milk. (See Notes.)

Using a fork, poke holes all over warm cake; slowly pour milk mixture over cake. Let cool completely. Refrigerate for at least 3 hours. Just before serving, spread Apple-Cinnamon Cereal Whipped Topping on top, swirling as desired, and garnish with cereal, if desired.