Learn French: Vous avez quatre pommes ou cinq oranges ? - Do you have four apples or five oranges?

Yes, the "q" in cinq is pronounced like a "k". Because oranges starts with a vowel, that "k" sound links directly to the next word. It flows together and sounds a bit like "sank-oranges".

Do numbers like quatre and cinq need an s at the end because there is more than one apple or orange?

No, French number words don't change their spelling when they describe plural objects. You write quatre and cinq, not quatres or cinqs. The only number that changes based on the noun is un (one), which becomes une for feminine words.

Do I pronounce the s at the end of pommes and oranges?

No, the plural s at the end of most French nouns is completely silent. You pronounce pommes exactly the same as the singular pomme. The listener only knows it's plural because they hear the numbers quatre and cinq.

Why does this question start with Vous avez instead of a question phrase like Est-ce que?