For the cinnamon-sugar donuts, let the donut maker warm up early. Mix eggs, sugar, vanilla sugar, a pinch of salt and cinnamon, freshly grated lemon zest and some lemon juice together in a bowl.
Add milk and oil and mix until smooth. Brush the donut maker with a little oil. Pour 1 tablespoon of batter into each donut pan and bake the donuts for about 3-4 minutes.
Continue this until all the batter is used up. Mix granulated sugar and cinnamon and roll the hot donuts in it.