Answer
1. If you are certain that water went down your throat unintentionally, your fast is broken. A Qadhaa will have to be offered after Ramadhaan.
2. No, it is Makrooh to use any form of toothpastes or powders whilst fasting. If the paste slides down the throat, the fast is nullified.
and Allah Ta’ala Knows Best
Mufti Muhammad Kadwa
FATWA DEPT.