chē shang yǒurén mài yǐnliào língshí shí, bù xiǎng mǎi jiù shuō 'búyòng, xièxie'

车上有人卖饮料零食时，不想买就说“不用，谢谢”。

When someone is selling drinks and snacks on the train, just say 'No, thank you' if you don't want to buy them