Dissolve the sugar and yeast in the warm water in a small bowl or measuring cup and let the mixture sit for 5 minutes, or until it becomes foamy on top. Combine the flour and salt in a large bowl. Use the paddle attachment on a stand mixer to mix the softened butter into the flour. If you don't have a stand mixer, use a mixing spoon to combine the butter with the flour. When the yeast mixture is foamy, pour it into the flour mixture and use a dough hook on your mixture to combine the ingredients and knead the dough for approximately 10 minutes. If you don't have a stand mixer, combine the ingredients and then knead the dough by hand on a countertop for 10 minutes. Place the dough in a covered container and let it sit for 1 to 1 1/2 hours, until it doubles in size. When the dough has doubled, measure out 2-ounce portions and roll the dough between your hands or on a countertop to form sticks that are 7 inches long. Place the dough on parchment paper-lined baking sheets, cover and set aside for 1 to 1 1/2 hours, or until the dough doubles in size once again. Preheat the oven to 400 degrees F. Bake the breadsticks for 12 minutes, or until golden brown. When the breadsticks come out of the oven, immediately brush each one with melted butter and sprinkle with a little garlic salt.