Root Beer Sloppy Joes on Pretzel Buns

Name: Root Beer Sloppy Joes on Pretzel Buns
Ingredients: 1 pound white bread dough; 1/4 cup baking soda; 2 egg whites; Pretzel salt, for sprinkling; Butter, for greasing; 3 tablespoons olive oil; 1 cup diced onions; 1 cup diced red bell pepper; 3 cloves garlic, minced; 1 pound ground beef; 3 teaspoons chili powder; 1 teaspoon dry mustard; 1/2 teaspoon cayenne; 1/4 cup tomato paste; 1 tablespoon Worcestershire sauce; 2 tablespoons maple syrup; 2 tablespoons red wine vinegar; 1 1/4 cups sassafras root beer; Salt