I guess I should have put more info. It was a wine kit, a chamblais. It was at terminal gravity. I sulfited it, added potassium sorbate, and finings. I have done the marble trick and I have some, however it will need a LOT of marbles.
I ended up adding a 1.5 L of the last batch of wine. It still is not topped up enough. I will probably just buy a cheap bottle of white to add. I wish there was some kind of calculation to determine how much to add. Or a calculation to figure out just how much dilution will take place by adding x amount of water. I would not mind diluting a tiny bit, but not a lot.
I guess next time I should rack it into a 5 gallon carboy. I guess that makes more sense. May lose a bit of wine, but better than having to worry about topping up a bunch.