Yeah I just watched it again to try and hear... but it's not possible for me. I can only assume that they are arguing about if 7up is better than Sprite.
Nero: 7up is way better
Dante: I think they're kinda the same dude
Nero: No way, try this! (drop kick)
Dante: That's it sonny, nobody drop kicks me and argues about soft drinks.
Nero: Hah, well now you've met your match.
Dante: A little Sprite now and then does make life more interesting, don't you think?
Nero: 7up was the original, Sprite is for sending guys like you back to hell!
Dante: Guys like me? I like 7up and Sprite about the same man.
Nero: Yeah guys like you, grandpa.
Dante: Grandpa? I'm 29 douche face. Now you don't get any 7up.
Nero: I can have 7up if I like.
Dante: Adios kid