4 sentences

1. 这种药水是按秘方配制的。

   zhè zhǒng yào​shuǐ shì àn mì​fāng pèi​zhì de.

   This liquid medicine is prepared according to a secret recipe.

   Source: Dong Chinese Dictionary

2. 这是我们家族祖传的秘方。

   zhè shì wǒ​men jiā​zú zǔ​chuán de mì​fāng.

   This is our family's ancestral secret recipe.

   Source: Dong Chinese Dictionary

3. 这个家传秘方从不向外传。

   zhè gè jiā​chuán mì​fāng cóng bù xiàng wài​chuán.

   This secret family recipe is never shared with outsiders.

   Source: Dong Chinese Dictionary

4. 这种老字号的秘方药膏声称能疗各种皮肤病。

   zhè zhǒng lǎo​zì​hào de mì​fāng yào​gāo shēng​chēng néng liáo gè zhǒng pí​fū​bìng.

   This time-honored brand's secret formula ointment claims to cure various skin diseases.

   Source: Dong Chinese Dictionary