1. Press quartered tomatoes through a sieve into a large bowl.
2. Add garlic, sugar, salt, pepper, and the 2 cups of tomato juice. Cover and refrigerate. (Stop here if you are working ahead.)
3. When ready to serve, taste and add additional seasonings, if necessary. If mixture is too thick, stir in additional tomato juice. Stir in sour cream until blended and smooth.
4. Serve chilled soup in cups or bowls, garnished with cucumber slices.