From Longman Dictionary of Contemporary Englishcan’t/don’t believe somethingcan’t/don’t believe somethingSURPRISEDused when you are very surprised or shocked by something I can’t believe he’s expecting us to work on Sunday! I couldn’t believe it when he told me what had happened.can hardly/scarcely believe something I could scarcely believe my luck. → believe
Examples from the Corpus
can’t/don’t believe something• When I saw the video, I was like, I don't believe it!• I can't believe you lied to me! 