Put eggs, 300 g sugar, oil and orange lemonade in a large mixing bowl. Mix flour and baking powder, add and mix everything well. Pour the dough onto a greased baking tray (approx. 25 x 40 cm in size; approx. 3 cm high rim) and bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for approx. 20 minutes. Let the cake cool down on a cake rack.
Drain the mandarins on a sieve. Whip the cream and 2 tablespoons of sugar until stiff, then pour in the cream firming agent. Stir the sour cream briefly, fold in the cream. Fold 2/3 of the mandarins into the cream and place on the fanta cake. Sprinkle with the remaining mandarins and spread everything lightly wavy. Sprinkle with cinnamon.