work fruitlessly
Cooking with sand is a Chinese idiom. Its pinyin is Chu ī sh ā ch é NGF à n, which means cooking with sand. It means it's hard but useless. It comes from Gu Kuang's difficult journey in Tang Dynasty.
The origin of Idioms
Gu Kuang, Tang Dynasty, wrote a poem: "if you don't work hard, you can't eat."
Idiom explanation
Cook with sand. It's hard work but useless.
work fruitlessly
find spiritual sustenance in sth. - tuō wù yù xīng