Bring water, kielbasa, and 2 whole cloves garlic to boil in a large pot; reduce heat to medium and simmer for 30 minutes. Remove sausage and pour liquid into a separate bowl. Cut sausage into cubes.
Melt butter over medium heat in the pot used to boil sausage; cook and stir leeks, onion, and minced garlic until vegetables are tender, about 5 minutes. Transfer vegetables to a blender; add about 1/2 cup reserved sausage water and blend until smooth, adding more water as needed.
Pour vegetable puree and remaining sausage water back into the original pot. Add bay leaves and bring borscht to a simmer over medium heat; remove and discard leaves. Whisk sour cream and flour in a bowl until smooth; gradually whisk into borscht until thickened. Stir dill and vinegar into soup and season with salt and black pepper.
Divide cubed sausage and chopped eggs into bowls; ladle borscht over sausage and egg.