In a sauce pan over medium-high heat, add vinegar, salt and sugar. Bring to a rolling boil and then let boil for 3 minutes. (Make sure to use a range vent or open window as boiling vinegar can be strong).
Add shredded cabbage to mason jar. Press down until all of it fits.
Pour boiling liquid over cabbage. Let sit on counter at least 30 minutes before serving. Once fully cooled, you can secure with lid and ring and store in refrigerator for up to 3 weeks.