The phrase "do time" is a common expression used to refer to serving a prison sentence. However, there are several other synonyms that can be used instead of "do time". Some of these synonyms include "serve time", "do a bid", "serve a stretch", "spend time" or "behind bars". Each of these terms can be used to describe someone who is incarcerated and serving a sentence. Utilizing these synonyms can add variety to your writing and speaking, as well as help avoid repetitive language. Regardless of which term is used, they all have the same meaning of serving time in prison.