Peel garlic, slice in half, discard the centre ‘germ’ and chop roughly. Place in a blender with ½ teaspoon salt and 4 slices of the bread and process until crumbed. With motor running, slowly add the oil until fully incorporated. Remove from blender and set aside.
Peel and quarter tomatoes. Seed one tomato, dice finely and set aside.
Remove most of the skin from the capsicums/peppers using a small knife or potato peeler. Halve capsicums and remove seeds and membrane. Dice half a capsicum finely and set aside.
Peel and halve cucumbers. Seed half a cucumber, dice finely and set aside.
Peel and halve onions. Dice one half finely and set aside.
Reserving the finely diced portions for garnish, place tomato, capsicum, cucumber and onion in the blender and process until smooth.
Add bread paste and process again. Add vinegar and process briefly to combine. Refrigerate, in blender, until well chilled, preferably overnight.
Meanwhile, cut remaining bread into small cubes. Heat a frying pan, add a drizzle of oil and fry bread until golden and crisp. Tip onto a plate to cool then store in an airtight container until needed.
Blitz soup one more time in blender, then pass through a fine strainer, pressing down with the back of a ladle to extract as much liquid as possible.
Stir water into the soup, adding more or less depending on the consistency you prefer. Taste and add extra vinegar or salt if needed. Return to the refrigerator until well chilled.
Serve topped with a scattering of diced vegetables and toasted bread cubes.