Vitamin water wit fizz

I bought a vitamin water today as i do everymorning. The water i only opened at 2 today from the fridge and it was actually fizzy and the water tasted like it jad gone sour+!! How unreal is that i actually took a picture of the drink and it made mee feel ill. I can not believe that my favorite drink has put me off i spoke to the people at the convienient store ,they also said that they have never seen anything like it before. IT IS SO SHOCKIMG!!!!!!