The 27-year-old has been on trial at Plainmoor and scored twice for the Gulls in a friendly appearance.
Torquay have handed Gnabouyou a non-contract deal until the end of the season.
Gnabouyou`s last club was Finnish side Inter Turku, for whom he has played four times in the Europa League, while he has also played in Malta for Sliema Wanderers, Greece for Kalloni and US Orleans and Paris FC as well as Marseille in his homeland.