"The cats drink the water."
Translation:Die Katzen trinken das Wasser.
Just want to complain a little about the hover hints... I thought it was ...das Wasser, and that "das" doesn't change in the accusative, but just to make sure I checked the hover hint. Die appeared on top. This usually does indicate the correct word for the sentence under examination. So I wrote it, and got it wrong... How do your write an emoji for frustration? :/ ?
Whether "cats" or "water" is the subject doesn't come into this. The article "the" is always linked to the word it "belongs to", they share the same number and case.
So, depending on the case, "Wasser" can be "das Wasser" (nominative), "des Wassers" (genitive), "dem Wasser" (dative) or "das Wasser" (accusative). In this sentence, the water is the object and takes (in this example) the accusative case: "das Wasser". The cats are the subject and take the nominative case: "die Katzen".
To use a different example where the changes in case and number might be clearer:
"der Hund" = the dog; plural: "die Hunde" = the dogs
"der Mann" = the man; plural: "die Männer" = the men
"Der Hund beißt den Mann." = "The dog bites the man." The dog is the subject and thus in nominative case. The man is the object and (in this example) in the accusative case.
Several dogs bite one man: "Die Hunde (nom.) beißen den Mann (acc.)."
(note: this is not a direct translation of the English sentence, but translates as "The dogs bite the man"; this also goes for the following sentences.)
One dog bites several men: "Der Hund beißt die Männer (acc.)." - the accusative case of "die Männer" is also "die Männer".
A man bites a dog: "Der Mann beißt den Hund." And several men bite several dogs: "Die Männer beißen die Hunde." - "der Mann" and plural "die Männer" are nominative case; "den Hund" and plural "die Hunde" are accusative case.
A cat bites a man: "Die Katze beißt den Mann." And several cats bite several men: "Die Katzen beißen die Männer." - "die Katze / die Katzen" is nominative, "den Mann / die Männer" is accusative.