Q:

What is a good way to clean the inside of a water bottle straw while on a multi-day backpacking trip?

When coming back from a day of hiking and eating I often notice that the top of the straw of my water bottle is dirty on the inside.  I've come across quite a few options to clean the inside of the straw with tools such as brushes, pipe cleaner, or a dishwasher. 
However, when on a multi-day hike, with only the equipment you can carry in your pack, these implements will likely not be on hand.  In the past, I've drawn some water up the straw on the cleaner side and blew the water out on the more dirty side.  This does help some but what I'm wondering is if there a more thorough way of getting the inside of the straw clean without the typical household items?
This questions assumes you didn't pack any replacement straws or little brushes, as shown below, specifically for this purpose.

Source: Amazon.com

A:

I would make an improvised bore snake with a piece of string or fishing line and a small piece of clean cloth and pull the piece of cloth through the straw just like you would a gun barrel.
Everyone should have at least some string and something like handkerchief which you might have to cut down to size in order to fit.
The other option would be to try and find a small straight stick and push a piece of cloth through but I think the bore snake idea would work better.

