The Messenger of Allah (may Allah's peace and blessings be upon him) used to sleep while in a state of Janābah without touching water

The Prophet (may Allah's peace and blessings be upon him) used to sleep after having had intercourse without having water touch his skin, neither the water of ablution, nor the bathing water, nor water even to wash his private parts, since the word 'water' here is mentioned in a general sense, so it includes all the uses of water.
The second possibility is that it means that he did not touch the water of ritual bath, not necessarily the water of ablution. This agrees with the Hadīths of the two Sahīhs that clearly state that he used to wash his private parts and perform ablution (when in a state of Janābah) before he would sleep, eat, drink, or have intercourse. One of such Hadīths is the Hadīth of Ibn ‘Umar in which ‘Umar said: "O Messenger of Allah, could any of us sleep while in a state of Janābah?" He said: "Yes, as long as he performs ablution." [Al-Bukhāri and Muslim]
‘Ammār ibn Yāsir reported: "The Prophet (may Allah's peace and blessings be upon him) allowed the one in a state of Janabah to eat, drink, or sleep after having performed ablution the same way one does before praying" [Ahmad and At-Tirmidhi]. However, the generality of the Hadīth refutes this interpretation.
It is better to say that the Prophet (may Allah's peace and blessings be upon him) would not touch water sometimes in order to clarify the permissibility of doing this, for if he had done that regularly, it would have been thought to be obligatory, and this was all done out of facilitation and alleviation for the Ummah.