Someone already tried.
A television commercial for the loyalty program displayed the commercial's protagonist flying to school in a McDonnell Douglas AV-8B Harrier II vertical take off jet aircraft, valued at $37.4 million at the time, which could be redeemed for 7,000,000 Pepsi Points. The plaintiff, John Leonard, discovered these could be directly purchased from Pepsi at 10¢ per point. Leonard delivered a check for $700,008.50 to PepsiCo, attempting to purchase the jet.