Traveling on business,what clothing for Sao?

If you're talking about daily wear (street clothes) then dress down it the Order of the Day. As casual as possible, jeans or shorts, flip-flops or tennis shoes, t-shirts, etc.

If you're talking about the workplace then dress slacks, blouse, maybe even an ascot or neckerchief or perhaps a business dress. Open toed shoes here.... a definite no-no. While in some larger companies in São Paulo, business suits are still seen, most places are considerably less formal.

Thank you!
my concern was more about the temperature as I have no idea what the weather is like at this time, so if I would be ridiculous with short leaves for example. Since you mention shorts I guess it's pretty warm then
Why no open toes shoes? is this socially unacceptable? I was thinking of high heels sandals

Warm? Don't forget that we're just into the first week of spring right now and here in the State of Rio de Janeiro it's already in the high 20s and low 30s during the daytime. Seasons here in the southern hemisphere are exactly the opposite to the northern hemisphere.

Sandals are perfectly acceptable street wear and on the beaches, but you'll rarely if ever see open shoes in the workplace, just a cultural thing really. Guess that it is sort of an idea that open high heels kind of remind people here of the other kind of "working girls" (if you know what I mean).

Despite their global reputation for scanty dress on the beaches and the near nudity of Carnaval, in the workplace Brazilians dress in a very conservative and traditional manner as far as business attire goes. Except for the fact that you don't see too many ties (except on Av. Paulista in São Paulo) you probably wouldn't be able to distinguish a Brazilian businessman from one in Paris, London, New York or Toronto.