Combine warm water (or beer), yeast, and sugar in a stand mixer bowl. Stir and let sit 5–7 minutes until bubbly.
Add flour and kosher salt. Using the dough hook, mix until combined, then knead on medium about 5 minutes until a smooth ball forms, adding flour 1 tbsp at a time if too sticky.
Cover and let rise in a warm spot about 1 hour, until doubled.
Knead briefly, divide into 4 pieces, roll into ~22-inch ropes, and shape into pretzels.
Whisk warm water and baking soda in a large bowl. Submerge each pretzel, then place in a greased or parchment-lined air fryer basket.
Air fry at 350°F for 6–8 minutes, flipping halfway, until deep golden brown.
Brush with melted butter and sprinkle with salt. For cinnamon sugar, dip buttered pretzels in a mix of 1/2 cup sugar + 2 tsp cinnamon.
Serve warm with your favorite dipping sauce.