Preheat oven to 400° and line a large baking sheet with parchment paper. Cut each biscuit into sixths and roll into balls. Place on baking sheet.
Add baking soda to a shallow bowl filled with warm water. Whisk until the baking soda is dissolved. Brush baking soda solution onto each piece of dough. Let set until the dough has dried slightly, about 2 minutes, then brush with about 2 tablespoons melted butter.
Bake until golden, 10 to 12 minutes. Let cool slightly.
Whisk together sugar and pumpkin spice in a medium shallow bowl. When the pretzels are cool enough to handle, toss in the remaining melted butter then toss in pumpkin spice mixture. Serve warm or at room temperature.