My Nestea Iced Tea is fizzy?

I just bought a case of Nestea Lemon Iced tea earlier this week because it's my favorite soft drink. But to my surprise, instead of the flat and smooth lemon iced tea I was expecting, they tasted like they were carbonated. Many of the cans in my newly bought case had a slight fizz to it, but not all of them. None of the cans have expired, and it's the new design. The blue can with the word COOL on it. I'm just wondering if there was something wrong with my drinks and if anyone else had the same problem. Should I drink it or throw it out? One of them tasted especially fizzy and i just threw that one out because I thought it might have something wrong with it. All the ones with the slight fizz, I'm a bit scared to drink. Is this okay to drink?