Preheat oven to 350 degrees F. Grease and flour two 9" round cake pans.
In a large mixing bowl combine sugar, flour, cocoa powder, baking powder, baking soda and salt. Mix well to combine.
Add eggs, milk, oil and vanilla to mixture. Beat with an electric mixer on medium speed for two minutes.
Carefully add instant coffee to boiling water and stir. Then carefully pour and stir in boiling water into cake ingredients. Mix until combined. The batter will be quite thin.
Pour batter into prepared baking pans.
Bake for 30 to 35 minutes or until a toothpick inserted into the center comes out clean and the top starts to spring back when gently touched.
Cool for 10 minutes then remove from pans and allow to cool completely on wire cooling racks.