Using one of your demitasse cups as a 2-ounce measure, fill the briki with as many cups of cold water as cups of coffee you want to make. Add 1 heaping teaspoon of coffee grounds for each 2-ounce cup of coffee. Add granulated sugar, if desired: 1 teaspoon per demitasse cup for medium-sweet (metrios_) or 2 teaspoons per demitasse cup for sweet (glykys_). For an extra-strong-sweet cup (vari glykos or glykys vrastos), add 3 teaspoons sugar and 2 teaspoons coffee grounds per 2 ounces of water. Heat over medium heat and stir just to incorporate the grounds and sugar. As the coffee heats, foam will rise. Be sure to hold onto the handle of the briki to keep it from falling over. When the foam nearly reaches the top, remove the briki from the heat and let it stand until the grounds have settled a bit, about 1 minute. Pour a little foam into each cup, then fill each cup, moving the briki up and down to help settle the grounds. Serve with a cold glass of water.