I don't know about Gdax, but Bittrex require KYC and to be honest its a little bit difficult for our documents to be accepted. Moreover there are no actual "Fiat" in Bittrex, they only have USDT which is not real fiat, though it backed up by USD. I think the best place to exchange is Quoine, you can check it in coinmarket cap for their pair here https://coinmarketcap.com/exchanges/quoine/ they provide real "Fiat (USD) to Alt" exchange. Then you can transfer it directly to your bank account via wired transfer.