If you already did it then adding more might make it taste like bubble gum as sorbate does have a taste although most people cant taste it at its recommended dosage.
Now there's an idea! You could even sprinkle a little yeast on it and see if it starts to ferment. If you can't get it to ferment, you added the sorbate. If it ferments, you did not.
I have a Muscat flavored with apricot puree going right now that I would like to restart fermenting. I know that I added the sorbate and I can't get it to restart for anything!