Well, "eat the spider the apple" doesn't make any sense, does it?
In order to ask a question in Danish, you only need to change the word order and move the verb to the beginning of the sentence. Unlike in English, you don't use a copula (do, be, have, …) for this purpose.
Edderkoppen spiser æblet. – The spider eats the apple./The spider is eating the apple.
Spiser edderkoppen æblet? – Does the spider eat the apple?/Is the spider eating the apple?