Yes, adding sugar should help, as long as it is concentrated. For instance, ciders, meads, and wines which have mostly simple sugars will often finish as low as 0.992. You can reap the same benefits of gravity reduction by adding sugar in a non-diluted manner. It might be best to make a simple syrup of 50/50 water to sugar by volume, or maybe 2:1 (somewhere in there), bring to a boil until fully dissolved, cool, and then add to your batch, to minimize water addition while ensuring sanitization of the sugar. You could add sugar directly to the fermenter without first dissolving it, but I'm not sure how well it would mix in that way. Even a syrup will need to be stirred or swirled in or it will settle to bottom.