Answered by: Alimah Siddiqa al-Farsiyyah
How should you wash dishes if a non-Muslim ate or drank in them?
بِسْمِ اللهِ الرَّحْمنِ الرَّحِيْم
In the name of Allah, the Beneficent, the Merciful
If a non-Muslim eats/drinks from a dish, the dish can be washed as normal. There is no need for extra cleaning as the essence (physical body/saliva) of a non-Muslim is not haram by default. This is mainly regarding the dish and not their leftovers. Their leftovers would also be clean provided that their mouth was pure of impurities.
Only Allāh Ta’ālā knows best
Written by Alimah Siddiqa al-Farsiyyah
Checked and approved by Mufti Mohammed Tosir Miah
Darul Iftā Birmingham
 Ascent to Felicity pg.65