Roughly chop the cucumbers, bell pepper, celery, and garlic then add them to a blender.
Add the spinach, walnuts, basil, sour cream, sherry vinegar, parsley, salt, sugar, and white pepper.
Pour in the water and olive oil.
Blend until the consistency of the soup is smooth.
Adjust seasoning to taste and place the soup in the refrigerator to chill until ready to serve.
If serving before the soup is completely chilled, add 1/2 cup crushed ice then ladle into bowls and serve.