Translation:I forgot the homework.
you ate the dog that's wearing the hat? If you wanted to say the homework was eaten by the hat-wwearing dog that would be 宿題は、帽子をかぶっている犬に食べられちゃった。
Apologies for the lackluster explanation, but it just doesn't sound right. Whose homework? What homework? Without "my" or "the", the sentence is too general, even though "to forget" seems to require a specific object.
Because that isn't proper English... I struggle with that sometimes as well.. I'm not a native speaker either.
Does it mean "I forgot what the homework assignment was" or "I forgot the homework at a place"?
How would the sentence change if the implied meaning was that you forgot about the existence/doing the homework?
You can use the duolingo sentence for that meaning ("I forgot to do my homework") or maybe a little more clearly as 宿題するのを忘れました (shukudai suru no o wasuremashita).