Whenever Messenger of Allah ﷺ went to answer the call of nature, I along with another boy used to carry a tumbler full of water (for cleaning the private parts) and a short spear (or stick).  

كَانَ رَسُولُ اللَّهِ ﷺ يَدْخُلُ الْخَلاَءَ فَأَحْمِلُ أَنَا وَغُلاَمٌ إِدَاوَةً مِنْ مَاءٍ وَعَنَزَةً يَسْتَنْجِي بِالْمَاءِ  

Whenever the Prophet ﷺ went to answer the call of nature, I used to bring water with which he used to clean his private parts.  

كَانَ النَّبِيُّ ﷺ إِذَا تَبَرَّزَ لِحَاجَتِهِ أَتَيْتُهُ بِمَاءٍ فَيَغْسِلُ بِهِ