Ramadan is special for so many reasons. That child who never prays, prays. That sister who never covers, covers. That brother who never fasts, fasts.
Even if it is just for one month, at least our non-practicing brothers and sisters will taste the sweetness of eman for thirty days. Surely, this ought to be a joy to behold knowing Allāh has chosen to guide these souls, whilst billions are still astray. And perhaps this coming Ramadan is what they need to help them overcome the barrier that enables them to become fully practicing. Look at what Umar ibn al-Khattab (may Allāh be pleased with him) said about how we should view our brothers and sisters that have wronged themselves:
“If you see that one of you has slipped, correct him, pray for him and do not help Shaytan against him (by insulting him, etc.).” 
Look back to when you started practicing and embraced the sweetness of eman. All it took for most of us was an event or incident in our lives that brought us closer to Allah. So isn’t it hypocritical for us to look down upon those who may well be Ramadan Muslims yet we ourselves were one of them too? Seriously, who are we to belittle, when we know Allāh is one who guides.
“And He found you lost and guided [you]” 
This coming Ramadan could be that event or incident for thousands of Muslims that makes them return to the obedience of Allah. So encourage them during this coming month. Welcome them into the Masjid, sit with them, eat with them and pray with them. Show them this is where they belong. Make them feel like the house of Allāh isn’t just for the fully practicing ones, but it’s for all. Show mercy and compassion. This is not the time to be envious or show signs of arrogance implying that you are better than them.
“It is enough evil for a Muslim to look down upon his (Muslim) brother.” 
If they come to the Masjid and make a mistake, do not be harsh with them, instead smile and explain things to them in the softest tone possible. How did the Prophet (peace be upon him) treated the bedouin who urinated in the masjid? Was he (peace be upon him) harsh and cruel? No, he (peace be upon him) used words of softness. And if you see or hear others saying words of discontent about them, then you should take it upon yourself to tell them not to do such a thing.
“A believer is the mirror of his brother. A believer is the brother of another believer. He protects him against loss and defends him behind his back.” 
This Ramadan could be a life changing experience for so many people and you could be that one person who has a big part to play in that. Be a source of guidance and steadfastness for them.
“And be, [O] servants of Allāh, bretheren. A Muslim is the brother of a Muslim. He does not wrong him. He does not fail him [when he needs him]. He does not lie to him. And he does not show contempt for him. Piety is here” – and the Prophet (peace be upon him) pointed to his chest three times. “It is enough of evil for a person to hold his brother Muslim in contempt. All of a Muslim is inviolable to another Muslim: his blood, his wealth and his honor.”