PhoenixWench wrote:

What I was wondering is whether it is possible, by feeding and nurture,
to make them produce more palatable fruit?

Not really without cross pollinating it with a palatable strain of
grapes. Some of the next generation seeds from a cross pollination
will produce a hybrid which may be tastier. Sow the seeds of the
tastier hybrid and you get a cultivar which may and may not be
significantly tastier. Who knows... ? It's all fun to experiment.