Does a smoker pee out "half a cup of tar"?

No. The claim confuses tobacco tar with nicotine breakdown products. The U.S. National Cancer Institute defines tar as a mixture of harmful tobacco-smoke chemicals that can form a sticky layer inside the lungs after inhalation. Laboratories measure nicotine and its metabolites, including cotinine, in urine—not “half a cup of tar.” The specific quantity is unsupported and biologically implausible.