In the bowl of a stand mixer fitted with a paddle attachment (or in a large bowl if mixing by hand), stir together warm water, yeast, and brown sugar. Let yeast mixture stand for 5-10 minutes or until foamy.
Once the yeast is foamy, stir in cinnamon, salt, and bread flour.
Stir in all-purpose flour 1/2 cup at a time until dough comes together. Dough will still be a little sticky. If you touch the dough, it should pull with your finger but shouldn't come off on your finger.
Cover the dough with plastic wrap, and let it rise for about 1 1/2 hours or until doubled.
Toward the end of the rising time, preheat oven to 425 F. Line baking sheets with parchment paper or silicone baking mats and spray with nonstick cooking spray.
To prepare the water bath, stir together remaining 2 cups warm water and 2 tablespoons of baking soda in a medium bowl.
Shape dough into knots, bites, or other desired shape.
Submerge dough in waterbath, and then place dough on prepared baking sheets.
Bake for 8-10 minutes for a 2-inch knot.
Toward the end of the baking time, melt butter in a small dish.
In a separate small dish, stir together sugar and cinnamon.
Remove pretzels from oven.
Immediately dip pretzels in melted butter and then into cinnamon sugar mixture.