Preheat oven to 350°. Bring first 3 ingredients to a boil in a medium saucepan over medium-high heat, stirring often. Remove from heat.
Whisk together flour and next 4 ingredients in a large bowl. Add soft drink mixture, and whisk until blended. Whisk in buttermilk, eggs, and vanilla. Pour batter into a lightly greased (with cooking spray) 17 1/2- x 12 1/2-inch sheet pan.
Bake at 350° for 18 to 22 minutes or until a wooden pick inserted in center comes out clean.
Prepare Fudge Icing, and pour over warm cake. Sprinkle with pecans. Cool completely in pan (about 1 hour).
United Tastes of Texas by Jessica Dupuy, copyright 2015, Oxmoor House.
This cake was so easy to make! The oil makes the cake itself super moist and the icing is amazing! We made it for Super Bowl Sunday and it was an instant hit. It is now my go-to cake for events. It is definitely a lot of cake and goes a long way for large parties. Highly recommend!