bad taste

Brought a coke zero 2liter at my local supermarket thinking I am going to enjoy it only to my utter disgust as I was pouring my glass a thin piece of black plastic floating inside the top, now I don't like complaining but if didn't notice it would have been a problem could have been the way the top was twisted when I opened it a piece of plastic of the top went into it, but this not on I almost drank it with the plastic, and sorry to say this coke has funny taste almost like its Pepsi cola I don't trust this coke taste I drink a lot zero coke because it helps with my diet but this definitely taste something like Pepsi the reason why I say this I had burgers in Burger King and has Pepsi it taste similar please check these branch I got it from