Preheat oven to 350 degrees F (175 degrees C). Spray a 9x13-inch baking pan with cooking spray.
Combine cake mix, 1 cup water, eggs, and oil in a bowl. Beat with an electric mixer until blended. Pour batter into the prepared pan.
Bake in the preheated oven until a toothpick inserted in the center of the cake comes out clean, 23 to 28 minutes. Cool on a rack, about 15 minutes.
Mix 2 cups boiling water and gelatin mix together in a bowl until dissolved. Stir in 2 cups cold water.
Transfer cake to a flat work surface. Cut out and discard the hard edges; crumble the rest of the cake onto the bottom of the baking pan. Spoon gelatin over cake; cover with bananas. Refrigerate until set, 2 to 4 hours.
Combine milk and pudding mix in a saucepan over medium heat. Bring to a boil, stirring constantly. Remove from heat and let cool until slightly thickened, about 10 minutes. Pour over the bananas. Layer strawberries on top. Chill trifle until set, 20 to 30 minutes.
Beat cream in a chilled glass or metal bowl with an electric mixer until soft peaks form. Spread over the trifle. Place cherries on top. Add pecans.
