Remove the crusts from bread and soak in 200 ml of cold water. Peel onions and garlic. Peel and wash the carrots. Cut everything into fine cubes.
Heat the oil in a pot. Fry onions, garlic and carrots for about 5 minutes. Season with salt and pepper. Remove the pot from the stove. Add tomatoes, bread, soaking water and vinegar and puree everything with a hand blender. Season to taste with salt and pepper. Chill the soup for at least 4 hours.
Season soup with salt, pepper, 1 pinch of sugar and lemon juice. For transport, fill into wide-necked bottles (e.g. from Weck) or thermos flasks. Place in a cool bag.