For the soup, in a bowl, mix the tomatoes, bell pepper, onion, cucumber, vinegar, garlic, olive oil, and bread. In batches, puree the soup in a blender on high speed, about 3 minutes per batch, until very smooth. Strain through a coarse strainer into a large bowl. Season with salt and pepper, place in the refrigerator, and chill for 1 hour.
For the garnish, warm the olive oil in a skillet over medium heat. Add the crushed garlic and cook, stirring constantly, until the garlic is golden brown, about 1 minute. Remove the garlic and discard. Add the bread cubes and stir to coat with olive oil. Cook slowly, stirring occasionally, until the bread cubes are golden, 10 to 12 minutes.
To serve, ladle the chilled soup into bowls and garnish with the croutons, bell pepper, cucumber, tomatoes, and red onion. Serve immediately.