"She does that once you sleep."
Translation:Zij doet dat zodra jij slaapt.
In English we use "to do" very frequently as an axillary verb (can, could etc.), especially in questions ("do you drive?") and in negative sentences ("I do not drive"). Most other languages, including Dutch, will just say "rijd je?" or "ik rijd niet" without any axillary verb.
Zodra triggers a dependent clause, which in Dutch has a different word order from the main clause: all the verbs go to the end of the clause. If there were any adjectives/adverbs/etc., jij and slaapt would be separated. For example, 'Zij doet dat zodra je lekker slaapt', or 'Ik zal je betalen zodra je me je naam, adres en bankrekeningnummer geeft'.