In GRU international transiting passengers can turn around hassle-free, though if your country of origin requires a visa for Brazil, the airline may require a visa to issue your boarding pass to GRU,

When you deplane you can simply pass through security and you're in the international gate area or go along all the way but instead of descending stairs towards immigration simply turn right/left, depending on the satelite you arrive, and head up one floor for the Lounges area or for the Duty-free shops.