How to exchange Bitcoin if you don't have fiat currency.
Without fiat bitcoin can also be used as currency or a means of payment, that is one of the basic ideas of bitcoin although a number of countries have not legalized it. Find a service that accepts bitcoin as a means of payment, you can transact with them.
Some countries prohibit the use of cryptocurrencies, restrict Bitcoin, and people can only use legal tender. In terms of payment methods, people usually use legal currency to pay. Most bitcoins are used for investment and storage.
When you are prohibited by your country and government from using bitcoin as a means of payment, then that does not necessarily make you unable to do so. Many people spend their bitcoin to pay for something even though it is illegal, however this can be done as long as you and the seller agree
[I do not recommend that you do it], but you can do it secretly.