If you want to make it sparkling and sweet at the same time, this thread will be invaluable
Essentially what you can do (there may be other options) is when it's finished fermenting, add your sugar/juice and get it tasting like you want.
Typically, you would add sodium metabisulfite (campden tablets) and potassium sorbate, which would critically stop the yeast from eating the additional sugar. Since it would essentially stop fermenting, there wouldn't be any C02 given off, and the wine would be still.
But, if you want sparkling, don't add the sodium or potassium. Bottle after you add the sugar/juice and make sure you add some to an old soda bottle. The soda bottle will be your "test." Whenever the soda bottle is firm (or before it gets to that point if you don't want much carbonation), you need to pasteurize ASAP, otherwise you will have bottle bombs on your hands. The thread above will help you a lot.
My only two concerns would be the cork's ability to hold in the CO2 during this whole process, and ensuring that the entire bottle reaches the necessary temperature to kill the yeast. Beer bottles are easy enough because they're pretty small, but wine bottles might be a bit more difficult.
...or you could probably use a keg and save yourself a lot of trouble