I've used fake hemp, used to dip it in the juice of the real stuff every cast - Caught a few fish but the majority said "Yeah right" as they turned away last minute
Same with rubber maggot, used it to avoid small stuff in big bunches on the basis there would still be something on the hook at the end of the trot but on it's lonesome it don't do too well.
Caught plenty of carp off the top using just a cork ball though among mixer
It's very interesting watching the fish turn their noses up at our poor attempts at deceiving them and it's safe to say some species have better eyesight than others who rely on smell or feel