I just read about this and thought it was kind of interesting:
Comerica Park has Vegetarian options- A vegan burger and veggie stir-fry. You can find the burger at the Brushfire Grill area by the Ferris Wheels. The veggie stir-fry is at the Asian Grill near the Big Cat Court, by the merry go-round.
It took TWO years of negotiations to get this to happen! How crazy is that? Next time you go to a game, make sure to get one of these items to show your support.
Also, one of the key groups in making this happen was VegMichigan, so make sure to check out their site and events also. It's kind of like Michigan Raw Food- only it's about Vegans and Vegetarians. They offer a lot of great classes and events: www.VegMichigan.org