(DISCLAIMER: Enjoy responsibly. 21 means 21. Don't drink and drive.)
With our trip up to Villanova, we asked our resident Philadelphia native for the classic Philly drink, and his answer didn't involve vodka, rum, gin, or any other alcoholic beverage. His answer was simple and clear.
Frank's Black Cherry Wishniak
If you want a brief overview of Frank's, just read this history lesson and you'll see why Philly natives go crazy over the stuff. For southerners, Frank's is the Philly equivilant of Cheerwine, a soda that was sent to the brink of extinction, but is slowly working its way back to relevance.
You can buy a 24 can case of Frank's through Amazon, but it'll set you back a cool 70 dollars. For those in the Bay Area, I would suggest heading to Subs and Such on Bearss and Livingston, who always have a nice supply of regional sodas for you to try.