Set the grapes in a hot, sunny spot, like the dashboard of a parked car. Let them sit and dry out for 4-5 days, rotating them at least twice a day. (This sun method works best in hot, dry environments.) If needed, cover them with a cheesecloth, or similar material, to keep them clean, but still allow airflow. Alternatively, you can dry the grapes in the oven for quicker results! Set the oven to 200 degrees and let the grapes dry out for about 2 hours. Rotate the grapes after one hour, so they evenly dry out.