Use sourdough starter once a week or stir in 1 teaspoon sugar. After using starter, replenish it by stirring in 3/4 cup all-purpose flour, 3/4 cup water and 1 teaspoon sugar until smooth. Cover loosely; let stand in warm place at least 1 day until bubbly. Cover tightly; refrigerate until ready to use. To use, stir cold starter; measure cold starter, and let stand until room temperature (starter will expand as it warms up).