According to the USDA new guidelines, they can be done without sugar. You can use plain water, or I used white grape juice cut with water. I just added water to the juice until it tasted good to me. I don't like super sweet stuff.
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During WW2, my Grandma would hot water can peaches, and since sugar was rationed, she did not use it. Just put in some whole cloves to keep the "ugh" taste away.