I think taking empty cans to the scrap yard is best idea just cuz you get cash back so you can buy new cans and caps and whatnot
Word to this, if you're going to ditch them in a trash can near the spot make sure to bury them down though, if a cop sees a paint can in the trash at taco bell he knows he could probably dust it for prints. Scrap them, dumpsters, public trash cans, stuff them up your ass, as long as you aren't leaving them at the spot, because that's some real fucking toy shit.
I seen a guy throw them in a stream or reservoir and he said the would just rust over, but I wouldn't recommend that, just because its bad for the environment. you could always wipe the prints off them and maybe throw them in a big dumpster or take them to a processing facility.
you could always save them and paint mini pieces on them with paint markers. the can could be a canves.