I love those reusable plastic cups with the lids and straws. I get them as gifts. I give them as gifts. I use them everyday.
At Christmas I got this one from a student:
The straw is see-through. I started to see mold growing inside the straw!!! Disgusting! Well, I brainstormed as to how to get this mold out of there. Here's what you need:
2. Long, skinny object that will fit through the straw, at least 3/4 of the way through
I have not been able to locate a long skinny object for quite a while, but yesterday I got my new character shoes for work, and holding the shoe apart was a long skinny object! That's the black thing you see down below. Skewers or skinny straws will work too, as long as they can fit in the straw.
Get the Q-tip and the inside of the straw a little wet. You might need to spread out the cotton on the Q-tip a little bit so it reaches the sides of the straw.
Stick it in, then push it through with the long skinny thing (ignore the dirty Q-tip, the other Q-tip is inside the straw).
Push it all the way through, then go back and forth a bunch of times.
This is how your Q-tip will look after going back and forth 10 times or so... yuck! You were drinking through that gunk!
Now rinse the straw, and drink with peace.