Is it possible to convert non-alcoholic wine to alcoholic wine by adding sugar and yeast?

Not a fundi but this will not seem practical as sugar and yeast are naturally occurring in wine though yeast is added. Non alcoholic wine usually has alcohol extracted by different methods as alcohol is the the result of sugar and yeast combining. Perhaps better to just add alcohol percentage of 11 -15% as per your preference which should be clean without and flavor enhancements.