[Resolved]  Mountain Dew — Diet Mountain Dew taste bad

About every other 2 ltr of Diet Mountain Dew I buy is bad and I am sick and tired of it! Now when I go to the store I make sure to look at the dates on them it seems to help for the most part, but today I opened one that said December 8th and it should of been fine but was not and it is not the place I am buying it at because I go to several different places to buy it, so that tells me it is the company. I don't know what you can do to make it better but it needs to be done!