Without all most 0 fees!!
The simplest but not the easiest method involves peer2peer both offline and online exchanging of bitcoin for fiat or other cryptocurrency you intend recieving. Both method are fees free. The P2P (online) exchanging doesn't involve the use of third parties in the form of escrow or exchanges although both parties involves in the transaction will have to pays miners fees to complete the transaction supposedly both parties are recieving cryptocurrency but if it's a crypto for fiat transaction, just the sender will have to pay the miners fees.
For the P2P (offline) exchange, paper wallet is been used, in this scenario you recieved or send the private keys of the wallet holding the fund involved in the transaction for crypto to crypto exchange or recieve fiat equivalent to the crypto sold. It's a very risky process that doesn't involve fees since the transaction are done offline but it's recommended to only transect with those you can trust.