I would have ordered the siwak
لَوْلَا أَنْ أَشُقَّ عَلَى أُمَّتِي لَأَمَرْتُهُمْ بِالسِّوَاكِ عِنْدَ كُلِّ صَلَاةٍ
Lawla an ashuqqa ala ummati la-amartuhum bi-s-siwaki inda kulli salah.
"If I were not to be hard on my Ummah, I would have ordered them to use the siwak before every prayer."
Narrated by Abu Hurayrah. Sahih al-Bukhari 887, Sahih Muslim 252
A short reflection
He hesitated to make a hygiene act obligatory. Notice the mercy embedded in the absence of the command, and pick up the siwak anyway.