Originally Posted by mgonbrewlab
Would the grape juice help to add extra body after refermentation? This is my primary reasoning for wanting to use juice vs. sterilized water.
No. It will ferment out, making more lees and then require another racking to get it off the lees. It will need to be topped up. If you top up with juice, fermentation will restart, etc.
I top up with either a similar homemade wine or a commercial wine to avoid diluting the wine if necessary. I generally make a larger batch than needed (scaling up) and keeping the extra wine in a growler or something just for topping up later on.
For a white grape wine, something like sauvignon blanc would be a good topping up wine. It can be a cheap wine- Little Penguin is $3 at my local grocery, and it's fine for topping up something like that.