Preheat the oven to 350°F (175°C). Lightly grease two 6-cavity donut pans with cooking spray or brush with a little coconut oil.
In a medium bowl, whisk together the almond flour, vanilla protein powder, baking powder, sea salt, and ground cinnamon until evenly blended and free of lumps.
In a separate bowl combine the maple syrup, eggs, melted coconut oil, almond milk, and vanilla extract. Whisk until the mixture is smooth and glossy.
Pour the wet ingredients into the dry and fold gently with a spatula until just combined. Do not overmix; the batter should be slightly thick. Let the batter rest 8–10 minutes so the almond flour hydrates — it will thicken a bit during this time.
Spoon the batter into a piping bag or a sturdy zip-top bag with the corner snipped. Pipe or spoon the batter into the donut cavities, filling each about two-thirds full for a light, fluffy rise.
Bake on the middle rack for 12–14 minutes, or until the tops are set and bounce back lightly when pressed. Avoid overbaking to keep them tender.
Allow the donuts to cool in the pan for about 5 minutes, then carefully invert onto a wire rack to cool completely before glazing.
To make the glaze, sift the powdered sugar and cocoa powder into a small bowl. Add 1 tablespoon of almond milk and whisk until smooth; add tiny amounts of milk (1/4 tsp) if you need to thin the glaze to a dip-able consistency.
Dip the top of each cooled donut into the glaze, letting excess drip back into the bowl, then return to the rack. Sprinkle with rainbow sprinkles if using. Let the glaze set about 10–15 minutes before serving.
Store leftover donuts in an airtight container at room temperature for up to 2 days, or refrigerate for up to 5 days. Rewarm briefly in a low oven (275°F) to refresh the texture.