Preheat oven to 180 degrees C. Grease and flour a 23x33cm cake tin.
In a large bowl, combine the flour, sugar, cocoa, baking soda, baking powder and salt. Make a well in the centre and pour in the eggs, coffee, milk, oil and vinegar. Mix until smooth: the batter will be thin.
Pour into prepared tin and bake for 35-40 minutes, or until a skewer inserted into the centre of the cake comes out clean. Allow to cool in the tin before slicing and serving.