Preheat oven to 350° degrees F. Liberally grease a 9x13 light metal rectangular baking pan with cooking spray; set aside.
In a large bowl, whisk together the sugar, flour, cocoa powder, baking soda, baking powder, and salt until just combined. Add in the vegetable oil, eggs, vanilla and buttermilk and mix on low until combined. Lastly, very carefully and slowly stream in the hot coffee with the mixer on low until fully incorporated into the batter. Pour the batter evenly into the prepared pan.
Bake for 25-30 minutes or until a toothpick inserted near the center comes out clean or with moist but not wet crumbs. Cool completely.
For the frosting: In the bowl of a stand mixer, cream together the butter, cocoa powder and vanilla extract until soft and fluffy, about 1 minute. Gradually add in the confectioners' sugar, about one cup at a time, alternating with little bits of the heavy cream. Frosting should be light and fluffy.
Spread the frosting evenly over the cake. Top with the Oreo cookie crumbs in an even layer. Arrange gummy worms over the top of the cake.