In a large mixing bowl, combine warm water, sugar, and active dry yeast. Let sit for 5 minutes until frothy. Stir in all-purpose flour and salt, mixing until a dough forms, then knead for 5–7 minutes until smooth.

Place kneaded dough in a greased bowl, cover with a towel. Let rise in a warm area for 45 minutes, or until doubled in size.

Punch down the dough, divide into 12 sections, and roll each into a 20-inch rope. Form a U-shape and cross the ends twice, tucking them under, placing mozzarella in the center.

Bring a pot of water to boil, add baking soda. Drop each pretzel into boiling water for 30 seconds on each side.

Preheat oven to 425°F. Arrange pretzels on a parchment-lined baking sheet. Sprinkle with coarse salt and bake for around 20 minutes until golden brown.

Brush baked pretzels with melted butter if desired. Allow to cool slightly before serving warm with dipping sauces.