John Cena didn't have his tag team like Triple H got D-generation X or in fact Hulk Hogan (John Cena's idol) got The Mega Power with Macho Man!
Well, if you're talking about in real life, it'll actually be Rob McIntyre. He was friends with Cena in college and he's at Hard Nocks South(Cena's gym) a lot.
If you're talking about in WWE, I'd probably say that his closest friend is either Bryan or Orton. Cena & Orton have had a lot of matches together, & it looks like they get along on-and-off the mat.
He gets along with most people in the locker room though. Contrary to the reaction that Cena gets, I've heard very few wrestlers say bad things about him as a person.
John Cena
i think it could be Daniel Bryan since they have gotten to know each other very well with Bryan married to Brie Bella and Cena dating Nikki Bella Bryan and cena likely spend most time together during Bella family dinners at the Bellas and double going on double dates etc
charity kids
The shovel