To make the brine. Mix water with salt, bring to a boil and dissolve the salt. Pour in the cucumbers, let cool at room temperature, and then refrigerate overnight..
Sprinkle the peeled onion and unpeeled garlic with a little oil and bake (the garlic is cooked faster, so don't forget to get it out earlier). For garlic at 220 degrees, it took me 5 minutes, for onions-15. Peel the garlic.
Squeeze the water out of the cucumbers.
Mix cucumbers, green olives, onions, garlic, olive oil and carbonated water (not mineral, you can just take water). Chop in a blender. The consistency can be adjusted by adding or reducing the amount of water. Put in the refrigerator for a few hours, so that the products "made friends". If desired, the soup can be rubbed to obtain a smooth texture.