Short answer: at New York Comic Con!
According to the interactive floor map, Pepsi will have one of the four booths located outside the show floor near the escalators which lead to the fourth floor River Pavilion. (The other three: Bandai Namco Amusement America, Nickelodeon/Nicktoons Network, and DC Entertainment.)
Here’s the listing from the NYCC website! [HTML edited for clarity]
What’s “Pepsi Perfect“? It’s the product placement Pepsi designed for Back to the Future Part II, as seen above in the screen shot. In the movie, Marty, Doc, and Jennifer travel to October 21, 2015, to save his future son from being arrested. While there, Marty enters an 80’s-themed diner and orders a $50 vitamin-infused Pepsi.
What’s being offered at the booth? What’s for sale? Time will tell. (I just hope Marty shows up on October 21, and saves us from this Biffhorrific 2015.)