What is the ruling on the fast of one who performed an incorrect ghusl after foreplay with her husband during Ramadan?

Foreplay, if it does not result in the emission of semen, does not necessitate ghusl (ritual bath). Ghusl is only obligatory due to penetration or emission. The fast of one who wakes up in a state of janabah (ritual impurity due to sexual activity) is valid, and he is only required to perform ghusl for the purpose of prayer.