Soak bread in 1/2 cup water 1 minute, then squeeze dry, discarding soaking water.
Mash garlic to a paste with salt using a mortar and pestle (or mince and mash with a large knife). Blend garlic paste, bread, vinegar, sugar, cumin, and half of tomatoes in a food processor until tomatoes are very finely chopped. Add remaining tomatoes with motor running and, when very finely chopped, gradually add oil in a slow stream, blending until as smooth as possible, about 1 minute. (to make a richer creamier broth add the full 1/2 cup oil)
Force soup through a sieve into a bowl, pressing firmly on solids. Discard solids. (I use a shinwa, but you can use anything with very fine wholes)
Transfer to a glass container and chill, covered, until cold, about 3 hours. Serve with a tray of toppings, chopped cucumbers, peppers, onions and jalapenos and allow guests to make their own.