Has he younger siblings he may be jealous of and in acting out he gets attention albeit negative attention, as tinkerbell said is there any problem at school, any bullying ?
It is possible it could just be the meds too. And margypops is right with some children punishing doesn't do anything. Maybe theres something else bothering him which is making him act out. Something he's not sharing with you. Whether it be school, home, friends. Children do tend to act out and do weird things when something is bothering them.
As I said I often feel its the meds at the root of it and all the punishing in the world wont help that in fact I do believe that too much punishing makes things worse and causes a lot of anxiety ..
He is on Focalin. Has been on Concerta and Adderall in the past. He maxed out the dosage with Concerta and I was not happy with some of the side affects with the Adderall. He has had other strange behavior in the past as well... chewing on sleeves and necks of clothing, chewing on his head/foot board, and chewing on the mini-blinds. We have taken away everything except for bedding, clothing and books. I did have him in counseling for about 3 months but didn't feel that we were making much progress with getting to the root of things. I feel like I have a feral child at times. Although he has been doing great in math and reading etc... there seems to be some sort of a disconnect when it comes to action/reaction. Almost like he doesn't have the reasoning factor...
First I would take away ALL of his toys. Even the ones he hasn't peed on. Leave only a bed in his room for awhile. Ground him. And don't give him any thing back till he earns them back. Him having ADHD is NOT an excuse. He knows what he did was wrong. My nephew (8) did something like that the last time I visited him. Only it was only his garbage can. And it was because he was too lazy to go down stairs. He also has ADHD. He denied it when his mom asked. And then I pulled him aside and he told me the truth. But he KNOWS I don't play. Have to try more disapline and go from there.
May I ask what med he is on, some meds do have affects on behavior, you may want to ask your Doctor about it, and whether the dosage needs adjusting or the med changing .