Cook ground beef in a large nonstick skillet over medium-high heat for 5 minutes, until browned, stirring occasionally. Stir in 3/4 cup water and taco seasoning. Reduce heat to medium-low and simmer 5 minutes, stirring occasionally. Stir in refried beans until well combined and heated through. Set aside.
In a medium-size bowl, mix together tomatoes, 1/2 cup of the scallions, the sugar, garlic salt and black pepper. In a second medium-size bowl, mix together 1-1/2 cups of the shredded cheese and the sour cream.
In an 8-cup clear bowl, layer half each of the beef mixture, tomatoes and sour cream mixture. Repeat layering. Scatter remaining 1/4 cup scallions and 1/2 cup cheese over the top. Serve at room temperature.