sah-kray du
Here's a breakdown:
* Sacre: "sah-kray"
* Du: "du" (pronounced similarly to the English word "dew")
Important note: The final "u" in "du" is silent.
This pronunciation is applicable to the phrase "sacre du" regardless of what word follows it. For example, in the phrase "sacre du printemps" (the sacred spring), it's still pronounced "sah-kray du" with a silent "u" at the end.