In a blender or food processor, combine sugar, vinegar, oil, Worcestershire sauce, ketchup and onion, and process until smooth. Set aside
Place bacon in a large, deep skillet. Cook over medium high heat until evenly brown. Drain, crumble and set aside.
Place eggs in a saucepan and cover with cold water. Bring water to a boil and immediately remove from heat. Cover and let eggs stand in hot water for 10 to 12 minutes. Remove from hot water, cool, peel and chop.
In a large bowl, toss together the spinach, water chestnuts, bacon and eggs. Serve with the dressing.