Separate the egg whites from the yolks. Beat the egg whites for 2-3 min., gradually add the sugar in several lots.
Once beaten well, add the yolks 1 by 1, then the oil in a thin trickle and the Fanta, while stirring nonstop until homogeneous.
Smear a cake form with butter and sprinkle with flour. Set aside part of the mixture, add the cocoa to it.
Pour 2-3 tbsp of the cocoa mixture into the cake form, cover with the white mixture. Then add the remaining cocoa mixture and white mixture at the end.
Bake in a preheated 356°F (180 °C) oven about 20 min., then lower to 320°F (160 °C) and bake until ready (to a dry toothpick).