A plant is not "dead" after being picked, it simply stops growing. The different compounds in the plant remain very much alive until the plant decomposes then it essentially becomes a different form.
The cells in the plant, though picked, still remain alive.
Whether or not you think it is possible that the gmo beets could continue creating more Sugar once ingested, I still believe it is noteworthy that gmo beets are programmed to be resistant to fungus. Internally this could mean that as the candida struggles to break the gm Sugar down (e.g would take longer) it would grow as it did metabolize the sugar, specifically so there would be more candida than sugar.