Question: What is your opinion concerning people who sleep throughout the day in Ramadaan? Some of them pray in congregation while others do not. Is their fast valid?
Answer: The fast of these types of people is valid and they have fulfilled their responsibility. However, it is very deficient and in opposition to what Allaah’s objective is behind fasting. Allaah says:
“O you who believe. Fasting is prescribed for you as it was prescribed for those before you in order that you may gain Taqwaa (fear and dutifulness to Allaah).” [Surah Al-Baqarah: 183]
And the Prophet (sallAllaahu ‘alayhi wa sallam) said:
“Whoever does not abandon false speech, acting upon that (falsehood) and ignorance, then Allaah has no need of him abandoning his food and drink.”
It is well known that missing the prayer and not showing any concern for it is not from Taqwaa (dutifulness to Allaah) nor is it from abandoning acting on falsehood. So it contradicts what Allaah and His Messenger intended by the obligation of fasting.
It is strange that these people sleep the entire day and then spend the whole night awake. Perhaps they may even spend the night engaged in vain pastimes that have no benefit or in doing something unlawful by which they would be acquiring sin.
So my advice to these individuals and their likes is that they fear Allaah and ask Him to help them observe the fast in the manner that He is pleased with, which is spending the fast engrossed in dhikr (remembrance) of Allaah, recitation of the Qur’aan, praying and showing kindness to the creation as well as doing other things mandated in the Religion.
The Prophet (sallAllaahu ‘alayhi wa sallam) was the most generous of people, and the most generous that he would be was in the month of Ramadaan when Jibreel would meet him and teach him the Qur’aan. So during this time, the Messenger of Allaah (sallAllaahu ‘alayhi wa sallam) would be more generous in spreading good than a pleasant breeze. 
 Reported by Al-Bukhaaree (no. 1902) and Muslim (no. 2308)
Posted from: Advice for those Fasting in Ramadaan (Q&A)
Imaam Muhammad bin Saalih Al-‘Uthaimeen
48 Su’aalan fis-Siyaam (binothaimeen.org). Al-Ibaanah.com