"At the crack of dawn" is a popular expression that means very early in the morning, typically at sunrise. However, there are plenty of other phrases one can use instead of this expression. Some of the synonyms for "at the crack of dawn" include "at daybreak," "at first light," "at the break of day," "with the sunrise," "early in the morning," "at the outset of the day," and "at the break of dawn." Each of these phrases can be used effectively in various contexts to describe the earliest part of the day, depending on the writer's preference and intent.