Learn Polish: Ta pizza bez sosu nie ma smaku. - This pizza without sauce has no taste.

The preposition bez (without) always requires the following noun to be in the Genitive case. The dictionary form is sos (sauce), and its Genitive form is sosu.

Why is the word for taste smaku here instead of smak? Is that also because of bez?

No, smaku is in the Genitive case for a different reason: the negative verb nie ma. In Polish, when you negate a verb that normally takes a direct object (like having a taste), the object switches from the Accusative case to the Genitive case. The affirmative is ma smak, but the negative is nie ma smaku.

I noticed both sos and smak take an -u ending in the Genitive case. Is that a pattern?

Yes! Both sos and smak are masculine inanimate nouns. In the Genitive singular, these nouns usually take either an -a or an -u ending. While there is no perfect rule, abstract concepts (like smak) and substances or liquids (like sos) very often take the -u ending.

Could I just say Ta pizza bez sosu jest niesmaczna instead of using nie ma smaku?