This fact is old, back from December:
Garrett Temple said #wizards  have given Bradley Beal the nickname, "Big Panda." Why? Beal: "Because I eat a lot, like a Panda bear."
— Michael Lee (@MrMichaelLee) December 17, 2013 
Somehow it took almost 5 months for someone to follow up on this. The Washington Post  has some details, including that he’s a “big pizza guy.”
Bradley Beal's Teammates Call Him Big Panda by Sports Talk Florida
“Whenever we go out to eat, he might get the biggest meal, and he’s gonna finish it,” Wall explained. (Pandas also apparently eat a lot.) “Sometimes I’m gonna be honest and I’m like, ‘Man I can’t finish, I’ve got to take it to go,’ ” Wall continued. “He finds a way to be the only one to finish his meal.”
“You got to get your second wind,” Beal chimed in.
“He finds his second wind,” Wall agreed. “It’s like playing in Denver, he finds that second wind and he keeps going.”