ARe you wanting to add more sugar to sweeten it some, or are you trying to bump the alcohol some? To sweeten it, you should wait a bit, rack it to a clean carboy, stabalize with k-meta and sorbate, let it sit for a few days and then you can add sugar to your taste. If you want to add to bump the alcohol, it mite take back off with a sugar addition. Mite need some energizer and nutrient, mite also need added yeast. This is assuming that the alcohol content is not so high it has killed the yeast off. Hope this helps, Arne.