substances or objects that must be mixed or added following a particular order to obtain a unique blend. a diary.
The purpose of all religions is to help us know God and to teach us ways of worshiping God. You can think of all religions as signs that point to God, the goal of religion is not the religion itself, it is God.
For this reason, if a person believes in God, then they have achieved the most important part of religion. As God says, if someone believes in Him, then He may forgive everything else that they did wrong:
Surely, God will not forgive the ascribing of partners to Him. He forgives whoever He will for anything other than that. Whoever ascribes partners to God has strayed far indeed. (Quran 4:116)
The best thing to do is to treat them like they are good Muslims, for you don’t know what is in their hearts and what their future potential is. Spend time with them doing whatever you do together (shopping? going to the park?). This may be enough to help them slowly come back to Islam.
You shouldn’t make the person your personal project by trying different strategies on them or by arguing with them about religious matters. If they want to become practicing Muslims again, they will do it at their own pace, when they decide to do it. All you can do is be a good and kind friend to them and leave the rest to God. As God says:
You cannot guide whoever you please: it is God who guides whom He will. He best knows those who would accept guidance. (Quran 28:56)