So Bitwise researched this and presented to the SEC when they were applying for their Bitcoin ETF back in january.
They found out that over 90% of the bitcoin volumes are indeed faked & came up with a list of top 10 exchanges with actual volume.
They cited 'Blockchain Transparency Institute' for this research... but the story is messed up. There's no information on who these guys are & CoinDesk later found out that Bitwise was involved as a partner. Now Blockchain Transparency Institute cannot be reached but their coin market data is still reachable here: bti.live.
But the question remains as to who Blockchain Transparency Institute is? Their data somehow supported the Bitwise presentation to say that Binance & Bitfinex are one of the top 10 trusted exchanges with actual volume.
There's an article which covers this story in whole detail here:
https://cryptowhistle.com/fake-volumes-of-cryptocurrency-exchanges-the-not-so-transparent-blockchain-transparency-institute/