1. Trim the hard, green outer skin off the watermelon rinds and cut rinds into small one inch cubes.
  2. In a large mixing bowl, mix the rinds, bottled water, and salt until the salt dissolves.
  3. Seal the bowl and store it in the fridge over night.
  4. The next day, drain water from the bowl, refill with fresh water and dump into a large saucepan.
  5. Bring contents to a boil and cook for half an hour.
  6. Drain water, add apple cider vinegar and sugar. Set aside.
  7. In a cheesecloth bag, add cloves, ground yellow mustard seeds, and crushed cinnamon sticks. Tie the bag and add to the sugar and vinegar mixture.
  8. Bring the mixture to a boil, remove from heat and let it stand for 15 minutes.
  9. Add the boiled watermelon rinds and boil again in the vinegar mixture until the rinds are completely transparent and the vinegar thickens with the sugar, about 50 minutes.
  10. Remove spices from the mixture. Then, spoon the rinds and syrup into canning jars, leaving some space.
  11. Process the jars by letting them stand in boiling water for 10 minutes.