I'm taking care of my 9 year old brother for a few weeks and I woke him up this morning for school, and he gave me SO MUCH attitude and he yelled at me to go away and let him sleep and he SMACKED ME. So I told him he can't have a donut for breakfast, he can have his cereal instead. Well now he is pissed the fuck off. He came into the kitchen while I was pouring his cereal and went straight for the donuts anyway, and screamed when I said no. I put them up out of reach and he keeps pointing there and whining. Like, come on, bud, I'm not giving you the fuckin donut. He does not deserve a treat, he's grounded, behind on school, and he didn't pack his lunch last night like he was supposed to. Now he's stalling on eating and whining at me and has murder in his eyes. What should I do? Do I let him whine himself out of it and learn to accept that he's not getting what he wants or do I put him in the corner?