Preheat oven to 450° with racks in upper and lower third. Line 2 rimmed baking sheets with parchment paper and dust lightly with flour.
On a large wooden cutting board or work surface, roll each into a 1/2-in.-wide rope, dusting lightly with flour if they’re sticky; then cut each rope into equal pieces about 2 ½ in. long (they’ll shrink a bit, but will expand again as they rest). Set on lined baking sheets and push the ends of each piece in with your fingers to square them off. Let rest in a warm place, covered with a kitchen towel, until increased in size by half, about 20 minutes.
Meanwhile, bring 2 quarts water to a rolling boil, covered, over high heat. Slowly stir in baking soda (it will foam up).
Drop several dough pieces at a time into boiling water solution and cook 20 to 30 seconds (any longer and they’ll taste metallic). After every batch, add ½ cup water and let return to a boil; this will happen in seconds.
With a slotted spoon, return dough pieces to parchment-lined rimmed baking sheets. Trim shaggy ends if you like. If making savory pretzels, sprinkle immediately with coarse salt. If making cinnamon pretzels, transfer to a large bowl, drizzle with butter, and toss to coat; then lift back onto baking sheets (reserve butter in bowl).
Bake pretzels until a rich, even medium brown and crackly on the surface, switching positions halfway through baking, 9 to 10 minutes. Meanwhile, mix cinnamon and sugar in a small bowl.
For cinnamon pretzels, transfer to bowl of remaining melted butter and toss to coat. Return pretzels to baking sheet, then sprinkle lightly with cinnamon sugar and toss to coat.
Serve pretzel bites warm, with dips.
*For vanilla glaze, sift 2 cups powdered sugar into a medium bowl. Add 10 tbsp. whipping cream and 1 tsp. vanilla extract. Whisk to blend. If it seems thick, whisk in another 1 tbsp. cream. Makes about 1 cup.