Meaning:
“我” means “I,” and “酸了” means “to become sour.” The use of “sour” here refers to the story “The Fox and the Grapes” from Aesop’s fables. The story concerns a fox that tries to eat grapes from a vine but cannot reach them. Rather than admit defeat, he states they are undesirable. Chinese netizens creatively use the saying to mean “I feel jealous of someone or something.”
Example:
A: 这个美女是谁?
Zhè ge měinǚ shì shuí?
Who is this pretty girl?
B: 凯莉·詹娜。她才二十一岁,是史上最年轻白手起家的亿万富翁,个人资产超过了十亿美元。
Kǎilì zhānnà。Tā cái èrshíyī suì,shì shǐshàng zuì niánqīng báishǒu qǐjiā de yìwàn fùwēng,gèrén zīchǎn chāoguò le shíyì měiyuán。
She’s Kylie Jenner. At 21, she became the youngest self-made billionaire ever, with personal assets surpassing US$1 billion.
A: 真厉害,我酸了。
Zhēn lìhài,wǒ suān le。
Good for her! I feel jealous of her.