Someone might say -Sa Sa fe?- or -Sak fe sa?- Do they mean the same thing?

These terms might have different meanings depending on context.
Besides the obvious, you can translate them this way too:
Kisa sa fè? (Sa sa fè?) - What does that matter?
and
Sa'k fè sa? (Kisa ki fè sa?) - Why?

If I were to use them in a sentence:

1. Sa sa fè si w pa gen soulye?  Ou kapab al legliz la pye atè.  Sa p'ap deranje okenn moun.
    Does it matter if you have no shoes?  You can go to church barefoot.  People won't mind.

2. -Mwen pa prale nan fèt la avèk ou jodi a. I will not go to the party with you today. 
    -Sa'k fè sa? Why is that?
    -paske m prale ak yon lòt moun. Because I'm going with someone else.



Haitian Creole ↔ English Reference, Look up Haitian Creole and English Words