The phrase "sucks in" can be replaced by a variety of synonyms depending on the context. For instance, one can use the phrase "absorbs" to describe the process in which something takes in another substance. Alternatively, one can use the term "inhales" to depict the act of breathing in. "Engulfs" is another suitable word that describes the action of completely covering and enveloping something. Another synonym is "devours," which is often used to describe the act of consuming or eating something quickly. Overall, there are numerous ways to say "sucks in" depending on the context and intended meaning of the phrase.