It depends on the amount of the water damage and the type of Bluetooth headphones. If the headphones have been thoroughly washed and dried, there is a chance they may still work. However, there may be some hidden damage which will cause problems after sometime.
If the headphones have been submerged in water for long period of time or exposed to a significant amount of moisture, it is unlikely that they will work properly again. In these cases, it is best option to consult a repair service or replace the headphones.