How can one convince friends who refrain from applying the Sunnah, such as letting the beard grow, avoiding Isbal (letting one’s garment hang below the ankles), and refraining from music, and who believe that religion is ease, to love the religion and the Sunnah?

Call people first to the established fundamentals of the religion, such as prayer, fasting, and hijab, and then call them to other matters, such as growing the beard and not lowering one's garment below the ankles. Explain to them the major concepts in Islam, such as the reality of servitude to Allah, the meaning of being content with Allah as Lord and Islam as a religion, and that obedience to the command of Allah and His Messenger is required by the reality of faith. Support your call with texts, be gentle and loving towards them, and supplicate to Allah for their guidance. Be patient with any hardship you may encounter, for the reward of da'wah (calling to Islam) is immense.