Preheat oven to 375 degrees F (190 degrees C) and spray a 6-well donut pan with unflavored cooking spray.
Bring Water (1/4 cup) to a boil. Stir in the Instant Espresso Powder (2 tablespoon) and let it dissolve in while you keep stirring for a minute. Take off the heat and let cool.
In a bowl, whisk together the All-Purpose Flour (1 cup), Dark Brown Sugar (1/2 cup), Baking Powder (1 teaspoon), Ground Cinnamon (1 teaspoon), and Salt (1 pinch).
Into the bowl of a stand mixer fitted with a paddle attachment, add the cooled espresso, Vegetable Oil (2 tablespoon), Vanilla Extract (2 tablespoon), and Egg (1). Mix them together on low until smooth.
Slowly pour in the dry ingredients as you continue mixing until you have a very soft batter.
Scoop the batter into a piping bag or a ziplock bag and cut the tip. Pipe the batter evenly among the 6 donut wells so that they are all a little over halfway full.
Bake for 10-12 minutes, until puffy and springy.
Let the donuts cool for 2-3 minutes once they are done, then turn them out onto a rack to cool some more.
Bring Water (2 tablespoon) to a low boil and dissolve the Instant Espresso Powder (1 tablespoon) in it just like you did before.
Pour espresso into the Powdered Confectioners Sugar (1 cup) and stir together. Pour in a Water (1 dash) to thin it out and make it an easily pourable glaze. If you find it too watery, just add a little more sugar.
Submerge the top half of each donut in the glaze and transfer them to a plate to harden.
Serve immediately, or keep for a day or two in a sealed container. Enjoy!