Preheat the oven to 350°F and lightly grease two 6-cavity donut pans (or one 12-cavity pan) with cooking spray.
Whisk the dry ingredients in a medium bowl: whole-wheat pastry flour, baking powder, baking soda, cinnamon, salt, and coconut sugar until evenly combined.
In a separate bowl, combine the wet ingredients: apple cider, applesauce, Greek yogurt, melted coconut oil, egg, and vanilla. Whisk just until smooth — don't overbeat.
Pour the wet mixture into the dry ingredients and fold with a spatula until no large streaks of flour remain. The batter should be thick but spoonable; if it seems very stiff, add a splash (1–2 Tbsp) of apple cider to loosen.
Transfer batter to a resealable plastic bag and snip one corner, or use a piping bag. Fill each donut cavity about three-quarters full for a uniform rise.
Bake for 10–12 minutes, rotating the pans halfway through, until the donuts are lightly golden and spring back when gently pressed. Let them rest in the pan for 2–3 minutes, then turn out onto a wire rack to cool slightly (about 3 minutes more).
While the donuts cool, stir the cane sugar and 1/2 Tbsp cinnamon together in a shallow bowl. Keep the melted coconut oil nearby for brushing.
Work one donut at a time: brush both sides lightly with melted coconut oil, then press and roll in the cinnamon-sugar until evenly coated. Place on a rack to set. Repeat with remaining donuts.
Allow the coated donuts to cool for a few minutes before serving. They taste best the same day but can be kept in an airtight container for up to 2 days.