It's important to understand that using this phrase is extremely inappropriate in most contexts and can be considered vulgar and offensive.
If you're looking for a word to use in place of "sonofa," it's best to choose something more polite and respectful.
For example, you could use:
* Darn
* Shoot
* Goodness
* Crikey
* Oh dear
Remember, choosing your words carefully is important for maintaining respectful communication.