Why does my dog always eat stuff she finds in the street?

This is not weird behavior but it is normal behavior. Dogs are opportunistic. This is why they survive so well. This is an instinct which is hard wired into the dog so you most likely will not be truly able to break her of the behavior. Spanking her won't help nor will removing the object form her mouth. She needs to learn a good leave it command. A step by step approach needs to be done just like any other type of training. The article below will give you a bit of help.