In a bowl, cover bread slices with cold water; let stand 15 minutes. Drain and squeeze water from bread.
In a food processor, combine tomatoes, sweet red pepper, 1 cup of the cucumber, the onion, garlic and 1/2 cup cold water. Process until very finely chopped. Add bread, oil, vinegar, salt and pepper. Process until smooth.
Transfer to a resealable container and chill for 1 hour. Garnish gazpacho with remaining 1/4 cup cucumber and, if desired, drizzle with additional olive oil and vinegar.
