sick like a dog字面意思“病得像只狗”，真实含义是表示某人“病得很重”。

【例句】
After stayed up late these days, he became sick like a dog.
因为这些天一直熬夜，他病得更厉害了。

He became sick like a dog and has gone to the hospital now.
他病得很重，现在去医院了。