There is no applications that really produce a free bitcoins nowadays, maybe there is some but they want something in return like advertising an ads or playing a game with your mobile phone and they only pay you a fraction of a bitcoin and that is not worth your time. If you see also mining of cryptocurrencies in your mobile phone then that is not profitable also because mobile phones are not design for mining.

Just take this in mind that there is no easy money wherever you go, if you believe to those websites that says to good to be true words is a sure scam because there is no overnight success in here and in the real world unless you do something illegal that can make other's life miserable.