Learn Polish: Ona nie lubi ciepłej wody gazowanej. - She doesn't like warm sparkling water.

This highlights the exact difference between descriptive and classifying adjectives. Ciepłej (warm) is a descriptive adjective that tells us a temporary state or opinion of the water, so it goes before the noun. Gazowanej (sparkling) is a classifying adjective that tells us the specific type or category of the water, so it belongs after the noun.

The verb lubić usually takes the accusative case. Why is woda in the genitive case (wody) here?

Because the sentence is negative (nie lubi). In Polish, when you negate a verb that normally takes a direct object in the accusative case, the object's case flips to the genitive. So while 'she likes water' is lubi wodę, 'she doesn't like water' must be nie lubi wody.

Why do both ciepłej and gazowanej end in -ej?

Because they are both adjectives describing a feminine noun in the genitive case. The feminine noun woda becomes wody in the genitive, and any adjectives modifying it must take the feminine genitive ending -ej.

Is gazowanej related to the word for gas?