If it is vinegar, it is pretty much impossible to get rid of, but entirely preventable.
Acetobacter takes hold in the presence of air. It's hard to see from the pic, but if you have left too much headspace after fermentation has finished, it could open the door to acetobacter infection (which creates vinegar). Brettanomyces and lactobacillus also like air. Sulfites displace oxygen, helping to prevent infection. I use them as minimally as possible, as I am very sensitive to their smell, which I find unpleasant, but they are handy. The more sound the fruit used, the less sulfites have to be used, and I think the tendency is for a lot of home winemakers is to overuse them, but that's just my opinion.