The full-back, who spent two seasons at Arsenal before leaving for Spanish club Celta Vigo in 2001, has won the Champions League twice and picked up three La Liga medals.
Hughes added: "Sylvinho has a wealth of experience at the very top level, having represented Brazil and played for some of the very top clubs in Europe."
City hope to include him in the squad to face Crystal Palace in the Carling Cup on Thursday, providing they receive international clearance.
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