The pronunciation sounds like a question. Is this how the sentence would be said even if when it is a statement?
No, it does sound like a question indeed. Happens with the computer voice somehow.
Is their an easy way to remember when to end ę or ą with in these situations?
For "kawę"? This is Accusative, for the direct object of the sentence.
Feminine nouns end with -ę. So does the word for "this": "tę".
Feminine adjectives, pronouns (so mostly possessives) and the word for "that" ("tamtą") end with -ą.