Preheat the oven to 350°F and grease and flour a 10x15-inch sheet cake pan.
In a medium sauce pan bring Coca-Cola, oil, butter, and cocoa to a boil.
In a separate bowl, mix the sugar, flour, and salt.
Pour the sugar mixture in the boiling liquid and beat well. Remove from heat.
Add the eggs, buttermilk, soda, and vanilla and stir well, until all ingredients are incorporated.
Pour into a greased and floured 10x15-inch sheet cake pan.
Bake at 350°F for 20-25 minutes. Prepare frosting while cake is baking.