As there is no upwards inflection at the end of the sentence to signify a question, like you do in English, what way can you tell this is a question and not a statement?
The question mark ?
Don't rely too much on the TTS voice.
The pronunciation and intonation is not always correct.
The volume of my computer is set at the lowest possible level, just enough to hear what she's saying, and to be able to report incorrect pronunciations.
Her voice is unpleasant, but that's just my personal opinion.
Ahh mine was a listening exercise.
Generally speaking would you expect a change in tone/intonation if it were asked as a question?
Yes, the tone of a question should be different than the tone of a statement.
When I listen to this sentence (pressing the blue speaker button on this page), the intonation is already more like a question.
Literally: You ask extra sambal? Can be translated to Are you asking for extra sambal or Did you ask for extra sambal or just You asked for extra sambal?. Depends on the context.