There is no such thing as free BTC, you may see some advertisement that will tell free Bitcoin but it is not. Well you can get Bitcoin when you exchange some free token that you can get from Airdrops. There are many free Airdrops that only require you to do some easy task like follows the telegram, twitter, facebook or alike. Also there are camapign, you can join to earn some tokens. Remember there is no such thing as free, you have to work for it.