Citizens Bank Park keeps is consistently voted the No. 1 Vegetarian Ballpark by PETA. I've had no problem eating there. I know they have vegan hot dogs and maybe some burgers and vegan chickn burgers? The crab fries are vegan and some of the soft pretzels are vegan.
Here's a link to their concession stuff which probably has more info: http://mlb.mlb.com/phi/ballpark/informa ... oncessions