I have been making wine at home for about 10 months. In a couple of instances it was not fermenting any more it was clear with little to no sediment. I added a little sugar to not back sweeten it per se but to see if it was really done fermenting or not. But as I said in a couple of instances as soon as the sugar hit the bottom of the carboy it's fizzed up like a shaken soda. I'm talking about seconds after adding the sugar not days. Any idea what that is?