In a small saucepan, bring the apple cider to a boil. Cook over high heat until the cider reduces by half. Allow it to cool completely.
While the cider reduces, whisk the flour, brown sugar, baking powder, kosher salt, baking soda, and spices together in a large bowl.
In a medium-sized bowl or a large measuring cup, whisk the eggs, cooled butter, and cooled cider together.
Make a well in the dry ingredients then pour the liquid ingredients into the well.
With a spatula, fold the flour into the liquid ingredients. Once a sticky dough comes together, cover the bowl with plastic wrap and place it in the refrigerator for at least 3 hours (overnight would be ideal).
On a plate or in a shallow container (I used a pie dish), thoroughly combine the sugar and cinnamon. Set aside.
Once ready, divide dough in half then on a well-floured surface, roll out the dough into 1/2-inch thickness and use a donut cutter to cut the dough (see notes).
Heat the canola oil in a heavy-bottom pot (I use a Dutch oven) to 375 degrees F.
Fry the donuts, 2-3 at a time, until they are golden brown (about 2-3 minutes on each side).
Place the fried donuts onto a paper towel to drain for a minute. Then immediately toss them in the cinnamon sugar mixture.