Beat the eggs well. Add the yoghurt, baking soda, oil and carbonated water. Add the feta cheese at the end.
Smear the tray very lightly with oil. Place 2 sheets, wrinkle them up slightly with your hands (so they're not smooth). Pour 1 ladle of the mixture on top. Continue in this order until out of sheets - 2 sheets and a ladle of the mixture.
Pour some of the mixture on the very top as well - make sure there's some of it along the sides and edges of the tray.
Cut the phyllo pastry into pieces and bake in a preheated 356°F (180 °C) oven for about 30 min.
After taking the ready phyllo pastry out, sprinkle it with cold water and smother with paper and a towel on top for about 5 min.