suspicious items in my dads personal bag?!

Yes, one can make a pipe out of a can doing just what you described! The can is crushed in the middle, right? That is where the holes might be and you can put your "smoking leaf" over the holes and use the hole at the top of the can to draw the smoke. Ive seen it done when I was a teen. Hope that sheds some light as to what this was used for...
But this information does not justify you going through things that are NOT yours to go through.

your dad is geekin. what they do is crush the weed up and put it over the hole in the middle of the can and then they take crack-cocaine and sit it on top of the crushed up weed and smoke it. you can smoke weed out of anything but the can is a dead giveaway for smoking crack-cocaine.

watching my cousin geek for the past 11 years

Yeah he was smoking cannabis. The black powder was ashes (i.e. combusted cannabis).

Tell your dad that he should get a glass pipe or smoke via a blunt or joint. Tell him smoking via an aluminum could cause him to develop Alzhimer's disease (maybe not, but why risk it?).

Also, don't worry about your dad. Marijuana is safer than tobacco, and studies show it can even help fight cancer.

Marijuana!
Empty Bottle is the Bong / piece
and the lighter is used to light the green substance.
Green substance is the marijuana ! :D

Not sure if this is a joke or not but yes, lots of people smoke pot through cola cans with holes in it.
Green stuff is marijuana.

He could be doing much worse things, like being an alcoholic.

its a bong lol, the green stuff is marijuana, yes it is a drug

me

maybe you should get your dad a real bong for christmas