Prepare the Oven: Preheat your oven to 300°F (150°C). Line a large baking sheet with parchment paper to prevent sticking and make cleanup easier. Spread the mini pretzels out briefly to check for any broken pieces, then place them in a large mixing bowl.
Make the Butter Mixture: In a small bowl, combine the melted butter and vanilla extract. Stir until evenly mixed. Pour the butter mixture over the pretzels, tossing gently with a spatula until the pretzels are lightly coated. Try to distribute the butter evenly without breaking the twists.
Mix the Cinnamon Sugar: In a separate bowl, combine the granulated sugar and ground cinnamon. Add the optional salt if you want a slightly stronger salty contrast. Stir thoroughly so the cinnamon is evenly distributed throughout the sugar.
Coat the Pretzels: Sprinkle the cinnamon-sugar mixture over the buttered pretzels in several additions, tossing after each addition. Continue mixing gently until the pretzels are coated on all sides. If some cinnamon sugar settles at the bottom of the bowl, toss the pretzels again to pick it up.
Bake Until Crisp: Spread the coated pretzels in a single layer on the prepared baking sheet. Bake for 20–25 minutes, stirring gently halfway through. Keep an eye on them toward the end of the baking time to ensure the sugar doesn’t darken too much. The coating may still feel slightly soft when the pretzels come out of the oven, but it will firm up as they cool.
Cool Completely: Remove the baking sheet from the oven and let the pretzels cool completely before serving. As they cool, the buttery cinnamon-sugar coating sets, helping the pretzels maintain their crunchy texture. Break apart any pieces that have stuck together, then transfer them to a serving bowl or airtight container.