Answer:
By choosing to end the sentence in a preposition.
Step-by-step explanation:
The best revision in the sentence could be the change in a preposition in order to avoid formal language that may provide an excessively sophisticated and complex. The employment of formal language often lessens the personal touch in the work. Thus in order to avoid this, the preposition could be replaced and the relative pronoun could be erased in informal language. Hence, the revised sentence would be as following:
"She didn't have the container to put the leftovers in."