All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
If that led each one of you to swallow the saliva of the other, then you have to make up this day. You should know that it is not permissible for a fasting person to do what breaks his fast, or could lead to the breaking of his fast. It is forbidden to cause the breaking of the fast, and what causes something forbidden is in itself forbidden as well.
Allaah Knows best.