Stop Marketing Illegal Drugs to Minors Act - Amends the Controlled Substances Act to impose increased prison terms on individuals who manufacture, create, distribute, or possess with intent to distribute a controlled substance that is flavored, colored, packaged, or otherwise altered in a way that is designed to appeal to a person under 21 years or age (or who attempt or conspire to do so). Provides for enhanced penalties for repeat offenses involving the marketing of methamphetamine to minors.