There are several synonyms for the phrase "get to work" that can be used to express the same sentiment. For instance, you can say "start working" to tell someone to begin their task at hand. Or you could say "get busy" to urge someone to focus and put in effort into their work. Another synonym is "roll up your sleeves," which means to tackle the task at hand with intensity. "Dig in" is also a great synonym that encourages someone to immerse themselves into their work and start producing results. Finally, you could say "put your nose to the grindstone" to remind someone to work hard and stay focused on their goals.