The phrase "sneak in" can be replaced with an array of synonyms depending on the context of the situation. Some common alternatives include "slip in", "creep in", "slide in", or "infiltrate". These phrases can be used to describe someone attempting to enter a place or conversation unobserved. Other synonyms for "sneak in" that convey a more subtle or deceptive connotation include "smuggle in", "conceal and enter", "secretly enter", or "slink in". The choice of synonym will depend on the desired tone, level of stealth, and intended purpose of the action being described.