Does bad breath allow a fasting person to pray at home, or must he break his fast to pray in congregation?

The change in mouth odor due to fasting is normal and does not prevent one from attending congregational prayers at the mosque. However, if the bad breath is strong and worsens with fasting, to the extent that it harms other worshippers, and it cannot be removed with a miswak or similar means, then you should not attend congregational prayers at the mosque. This is based on the prophetic narrations that prohibit those with unpleasant odors from attending the mosque, for the angels are harmed by what harms humans. Jurists have explicitly stated that strong bad breath is akin to garlic and onions in this regard.