What LC said, the main reason for adding lots of sugar in canning was to make the fruits safer. During WWII, they tended to become even sweeter (in the UK anyway) because if you have at least 1/2 sugar to 1/2 fruit you have pretty much made preserved candy. You can water bath can sweet fruit with no added sugar, but if you have to can it (rather than freeze) you might want to try pressure canning or try making wonderful peach "rollups" if you a deyhdrator.
expatriate Californian living in rural Ireland with husband, dogs, horses. garden and many, many cats