Whenever the Prophet ﷺ intended to sleep while he was Junub, he used to wash his private parts and perform ablution like that for the prayer.  

كَانَ النَّبِيُّ ﷺ إِذَا أَرَادَ أَنْ يَنَامَ وَهْوَ جُنُبٌ غَسَلَ فَرْجَهُ وَتَوَضَّأَ لِلصَّلاَةِ  

ʿUmar asked the Prophet ﷺ "Can anyone of us sleep while he is Junub?" He replied, "Yes, if he performs ablution."  

اسْتَفْتَى عُمَرُ النَّبِيَّ ﷺ أَيَنَامُ أَحَدُنَا وَهْوَ جُنُبٌ قَالَ نَعَمْ إِذَا تَوَضَّأَ  

ʿUmar bin Al-Khattab told Messenger of Allah ﷺ, "I became Junub at night." Messenger of Allah ﷺ replied, "Perform ablution after washing your private parts and then sleep."  

أَنَّهُ قَالَ ذَكَرَ عُمَرُ بْنُ الْخَطَّابِ لِرَسُولِ اللَّهِ ﷺ أَنَّهُ تُصِيبُهُ الْجَنَابَةُ مِنَ اللَّيْلِ فَقَالَ لَهُ رَسُولُ اللَّهِ ﷺ تَوَضَّأْ وَاغْسِلْ ذَكَرَكَ ثُمَّ نَمْ