During my travels, I have picked up many weapons such as LAMs, 12 Gauge Shotguns and Crowbars. These items have [clear uses](http://gaming.stackexchange.com/questions/13892/can-i-kill-everybody) and need no introduction.

Then there are some other items, such as...Soda, Chocolate Bars, and Soy Food? Clearly, these are not the tools of the trade of a hardcore killing machine...or indeed, of anybody at all, and the game offers no explanation for their existence.

Are these items only pickup-able for the sake of atmosphere and to fill those lonely gaps in my inventory, or do they actually serve a purpose?