You might have heard in recent weeks that Activision and PepsiCo have partnered on a deal that will offer Call of Duty: Modern Warfare 3 players some kind of double XP reward with the purchase of select products. The website devoted to the promotion has been updated with an official rules page which runs through exactly how you can get your double XP and how long it lasts.
The details get a little confusing, but it appears that there are different codes for different products. A 20 oz. bottle, 12-pack or Wal-Mart-exclusive 20-pack grants you 15, 45 and 90 minutes of double XP time, respectively. There are also rewards for combo purchases of both Dew and Doritos together.
Basically: buy specially marked PepsiCo products from the Mountain Dew and Doritos brands and get up to 90 minutes of double XP time in MW3 in return. The max amount of time you can accrue for one online ID is 24 hours. You can start collecting and redeeming codes as early as October 10. Maybe go on a diet until then?