Because THC is fat soluble, high fiber foods may help to bind up and eliminate THC. No one drink is going to help better then any others, go for what you can drink copious amounts of.
there are no foods to help flush it out, and water is the best drink for that. the thc sticks to your fat cells though, so no sugary drinks, like mountain dew.
White tea may help, as well as plenty of fruits and vegetables. Water will help flush everything in general. However, there are no quick fixes if you have a drug test coming up. Especially if they check the hair follicles.