For every quart of grape juice that you want to make; add 1 cup grapes and 1/2 cup sugar to a quart jar. Fill the remainder of the jar to 1/2 inch from the top with boiling water. Put on the lids (that were soaked in hot water for 5 minutes) and the rings. Put jars in a canner, cover with hot water. Bring canner to a boil; boil for 15 minutes.