The molecules of which foods are made are too large to pass through the lining of the digestive system. Digestion results in the formation of smaller molecules that are able to pass through that lining and enter the person's bloodstream. (for example,) Sugar molecules formed by the digestion of starch enter the bloodstream.
Either way, not worth the risk - you can get very ill from consuming or drinking expired products, including ice tea. Now if it is a best before date, that tells us something else. It says it has not turned or gone bad, but that it may not taste very fresh after the date on the bottle. There is a huge difference between the comments expired and best before - so please use caution and consider these points. For dry ice tea mix, you usually see a best before date.
Pre-sweetened ice tea is bad and ice tea should not have sugar added to it anyways. Soda pop is the most unhealthy because of the sugar and calorie content its ok to have a pop once in awhile however it just causes your body to retain fluid and weight because of the sodium,sugar and other additives. Soda pop is the worst, then iced tea then sweet tea. Pop contains lots of sugar and calories, and it bloats you. The main reason iced tea is bad is because of the added sugar. Sweet tea is a pretty good choice, but water, vitamin water and milk are much better .