To be in a foul mood / To be mean-spirited
Colloquial. Literally 'to have bad milk'. Describes someone who is grumpy, unpleasant, or nasty. Common in Spain, mildly vulgar.
He's in a really foul mood today, better not say anything to him.
That comment was really mean-spirited.
—Why did she answer you like that? —She's always mean-spirited.