Some people might think that because of the religion they will not find certain kind of amusement on the city. That is not truth. Those people are right when they think about religious matter, but anyway those very religious people are not part of the night life in Istanbul and they have their own kind of amusement that we also talk about Tea gardens.
Islam forbids consumption of alcohol, but you can find beer, wine and a special national alcoholic drink called Raki (*same as Uzo for the Greek, Arak for the Arabs - it is a 35C alcohol, which is deluded with water turning from transparent into a white drink. If you enjoy alcohol try it ! ).