How long does shake and bake meth stay in your system? my brother swears he is clean but it's still showing up in his system.

Only several days: Even in very heavy long-term users, methamphetamine and its metabolites are relatively short-acting, and will give positive urine drug test for 3-4 days at most. False positives for amphetamines, however, are very common, and may show up + with virtually any medication used for colds - sudafed, ephedrine, (ephedrine sulfate) phenylephrine and others. Confirmatory tests, however, should be negative.