The easiest/cheapest way to get to SP from the airport (and vice versa), the bus service has…read moreseveral lines but the only one that I have used so far is the one that begins and ends at Maksoud Plaza.
For around 45 reals (they advertise 42, but I was once charged 50, once 45 and a couple times it was actually 42) you get a very clean, comfortable bus, with free wifi (that actually works!!) and transportation to the area of the city that you need to be in. For some reason, GRU does not have a metro stop and so this is my preferred method of escaping the airport. (Just be aware that if you are on an international arrival, you will need to go to one of the other terminals to buy your ticket as they seem to only arrive at and leave from the domestic terminals for some reason.)