www.hoccabar.com.br

So, why should you go there? Main reason: because it's located in the city market: great architecture, historical spot, amazing many different foods to buy(I found mole, jalapenos and many different spices there) and last but not least the most famous pastel and sandwich in town.
If you come to Sao Paulo it's a must do. Forget the crowd and enjoy the food!!!
My favorite: Sol (carne seca, cheese and sun dried tomatoes)
But the most famous is Belissima and the Pastel de Bacalhau (Cod Fish)
Have fun and enjoy the view! But... arrive as early as possible!