Cream sugar with eggs and vanilla sugar.
Add the flour and baking powder mixture alternately with the oil and water.
Put half of the mixed mass into a greased mold, mix the other half with the cocoa powder and also put it into the Gugelhupfform.
Run a chopstick through the mixture in a wave-like pattern to create a nice pattern in the dough.
Bake the marble cake at 180 °C for about 1 hour.