In a saucepan, bring coca-cola, margarine, cocoa and oil to a boil. In a separate bowl mix sugar, flour and salt then Pour into the boiling mixture and mix well. Add eggs, buttermilk, vanilla and soda and mix well. Pour into a greased and floured sheet cake pan (9x13) and bake at 350 degrees for 20-25 minutes.
For Frosting: In saucepan combine margarine, cocoa and milk and heat until the butter melts. Beat in the remaining ingredients and spread onto HOT cake. Cool and cut.
Recipe by About a Mom at https://www.aboutamom.com/cracker-barrel-double-fudge-coca-cola-cake-recipe/