There are several synonyms for the phrase "break the seal." One alternative is "unseal," which means to remove the seal or break the closure of something. Another synonym is "open," which refers to the act of removing a cover or breaking a seal to access something. "Crack open" is also a suitable synonym, meaning to create a small opening or fissure in a seal or container. "Bust open" and "smash open" are more forceful synonyms for break the seal. However, it should be noted that these latter terms may connote intentional damage or destruction and are not always appropriate in certain contexts.