Sometimes it’s hard to say no, especially when someone is offering you something with good intentions.
Here’s a useful phrase to say no in a gentle way: “Daijoubu desu” or “Kekkou desu”, which means “No thank you.”
(“daijoubu”– ok/good, “kekkou” – good, “desu” – am/is/are)
Please note that these phrases also mean “I’m good” or “that’s good” depending upon the context. Chances are that these are not good enough to get your point across. If that’s the case, you need to just say “irimasen” or “hitsuyou arimasen,” which means “I don’t need that.” (“irimasu/iru” – (I) need~)
See you in the next episode of Speakin’ Japanese!