心非柠檬天然酸心非薄荷天然凉
[xīn fēi níng méng tiān rán suān xīn fēi bó hé tiān rán liáng]
The literal translation would be 'Heart not lemon is naturally sour; Heart not mint is naturally cold'. A metaphor expressing that although their inner feelings are similar in nature (like the characteristics associated with lemons and mints), but actually not, just fake or unreal expressions. In fact, such kind of heart feels nothing.