Family Tested & Approved
Combine sugar, flour and cinnamon in a large bowl and mix well using a wire whisk. Combine butter, coca cola and cocoa in a pot on the stove and bring to a boil stirring often.
Remove from heat and pour over flour mixture. Mix with a spoon. Mix buttermilk and soda together and pour into cake mixture.
Add marshmallows and continue stirring. Your marshmallows will not melt. Add in eggs and vanilla extract.
Pour into a sprayed 9x13 pan and bake in preheated 350 oven for 30-35 minutes testing for doneness. Frost.