Saliva might not be the grossest human fluid, but it is still pretty foul.

One particularly undesirable brand of spit is known as "backwash". Backwash is the term for fluid which makes its way from ones mouth back into a beverage container.

Backwash seems inevitable. There are some people who believe that the final 10%-33% of liquid in a soda can is backwash*. 

Can backwash be prevented, and are some beverage containers backwash-proof?

One evening, we endeavored to find the truth with a simple test:

First, we would richly color our mouth and saliva with a hearty dose of unsweetened Kool-Aid mix. Second, we would drink a bit of clear water from a test container. With our bright red saliva, it would be easy to see if saliva had made its way back into the drink.

In preparation, we set up five different drinking vessels and readied fresh packs of Cherry Kool-Aid Mix.

Ashley was first. She tore open her first packet of Kool-Aid.

Unsweetened, Kool-Aid mix is extremely tart and extraordinarily red. Kool-Aid is a summertime favorite for two reasons, it is cold, and it is sweet. Curiously, the Kool-Aid product does not actually possess these properties in its native state. You have to add the cold and the sweet yourself.

The shock of so much unsweetened Kool-Aid sent Ashley reeling. She looked as if she had just been struck in the face by a shipload of red lemons.

Luckily, she regained her composure, and was ready to test the first container.

She drank from a glass of water through a straw.

Sure enough, when her suction stopped, the water fell back down the tube, and with it came a little swirl of red backwash.

It dissipated before I could capture it in a photo. There was not much backwash at all. 

Ashley could hardly wait to spit. 

Ashley's reaction to the experience looked pretty intense.

The other test subjects volunteers braced themselves for a long, sour night.