If you love a street food festival then you will adore Smorgasburg, it's held at a number of different locations around New York during the summer months. I visited the one on the banks of the East River in Williamsburg.
You can find food for every possible cuisine and even diet! There were vegan stands, gluten free options etc etc. I guess seeing as it is New York each stand will probably cater for every eventuality or at least try and cater for some diets.
While you're there you should definitely check out Ramen Burger, quite literally heaven in amongst deep fried noodles. Mmm health.
You must also try a fresh Mango lemonade, as pictured in the title. You'll also find all manner of sweet treats or salads if you're that way inclined. You can take your newly purchased food and eat on the banks of the river with the gorgeous view of Manhattan glimmering along the skyline.