Preheat the oven to 200C. Lightly grease a donut baking form and set aside.
Grate the zucchini and squeeze out as much water as you can using a kitchen towel. Set aside too.
Mix the flaxseeds with 3 Tbsp water and let soak for about 10 minutes.
Meanwhile add the flour, cacao powder, ground hazelnuts, baking powder and soda and coconut sugar to a bowl.
In another smaller bowl stir together the sparkling water, milk, almond butter, apple sauce and ready made flax egg.
Combine the wet and the dry ingredients until a smooth batter forms. Add the zucchini and mix again.
Fill the donut molds and bake for 12-15 minutes. Let cool completely before removing from the tray. Repeat until there is no more batter left.