Trying to stay fit what should I take?

I'm trying to stay fit cause I'm trying to get back to play soccer again. So my question is what should I take or do so I can clean out my body from the junk food I have ate??? Also Ive seen people who are skinny and all of a sudden they get big like not dat but big like buff. I know is its drunk they drink to get them that. What drink do you recommend me????