Hi!
Artificial sweetener is one way, but I hate the after-taste.
I, too, made a batch of ginger beer that was drier than a pommie's towel. I considered making up a syrup buy adding sugar to some of the ginger beer and keeping it refrigerated so that it didn't ferment any further, then adding it to each glass that I poured.
Unfortunately the batch was spoiled when I lost CO2 pressure while on holiday, so I never got to test my idea.