Boil cranberries. In a large pot, add the water and cranberries. Place over medium heat and bring to a boil. Reduce heat to a gentle boil and allow it to boil until the cranberries burst, about 5 minutes.
Strain. Transfer the mixture to a dampened jelly bag or a fine mesh strainer and allow it to drip into a large bowl undisturbed for about 2 hours.
Prep for canning. Prepare jars for canning by washing them with hot, soapy water. Rinse and transfer them to a water bath canner. Fill the canner with water until the jars are fully submerged in the water bath canner. Place over medium-low heat, cover, and simmer. Wash your lids and rings, place them on a towel, and set aside.
Add sugar (optional). In a large pot, add the drained cranberry juice and sugar (if using). Add 1 tablespoon for every cup of liquid if you’re adding sugar. You can adjust the sweetness to your preference. Stir the sugar until combined.
Cook juice. Heat the juice until it hits 190℉. Cook for 5 minutes.
Fill jars. Transfer the hot jars to a heat-safe area and place a funnel on a jar. Ladle the hot juice into the hot jars, filling to a 1 inch headspace.
Debubble and wipe rims. Using a debubbler, remove any bubbles that may be in the jars. Top off with hot juice, maintaining a 1-inch headspace. Wipe the rims with a damp towel.
Process. Place the lids and rings back on. Tighten the rings until they are fingertip-tight. Transfer the jars to the water bath canner. Fully submerge the jars in water so there is 2-3 inches of water above the lids. Cover and place over medium heat. Bring to a full rolling boil. Once the water hits a full rolling boil, set the timer for 15 minutes.
Cool. Once it’s processed for 15 minutes, remove from the heat and remove the lid. Allow the jars to sit in the water for 5 minutes. Transfer the jars to a heat-safe area and allow them to cool for 12-24 hours.
Check seals. After 24 hours, check the jars for a proper seal by pressing down on the lid. If it does not pop up, it is good. If it does pop up, it did not seal. Once a proper seal has been confirmed, remove the rings and store the jars in a cool, dark place for 12-18 months or per your lid manufacturer’s recommendations. If a proper seal has not been confirmed, place the juice in the fridge and use within 5 days.