To be frank is a commonly used phrase that indicates honesty and openness in communication. However, it's important to have a variety of synonyms to avoid repetition in our language. Some great alternatives to "to be frank" include "to be honest", "in all honesty", "to tell the truth", "in truth", "in all truthfulness", "to be sincere", "frankly speaking", "candidly", "bluntly", "plainly", "forthrightly", and "transparently". Expanding your vocabulary with these synonyms allows for more dynamic and interesting communication while still conveying honesty and sincerity.