Preheat oven to 350 degrees.
In a medium-sized saucepan, combine the sugar and flour. Add in the mango, eggs, and unsalted butter and stir gently to combine. Heat over medium-low until thickened, stirring constantly, around 10 minutes. Remove from heat and set aside.
In a large mixing bowl, combine the cake mix, pudding mix, eggs, and oil and beat well to combine. Add in the 7UP and beat for 2 minutes on medium speed until smooth. Pour into a greased 9x13 pan and cook for 30-35 minutes, or until a toothpick inserted into the center comes out mostly clean. Remove from oven.
Spread mango topping over warm cake, then cool on a wire rack. Enjoy!