After finding my CamelBak bladder rust stained from the metal coat hanger I previously used to dry it, I thought there had to be a better way. I thought I remembered a site where somebody modified a plastic coat hanger. I After some searching I found it here: http://www.fightingreality.com/blog/?m=200606.
Plastic it definitely a better material, but I thought I could do better.
Step 1: Materials
Sharpie or other marker
Step 2: Measure
Measure the opening with an index card to get a rough size.
Trandsfer the measurement to the hanger.
Step 3: Bend the first side.
Using a heat gun, heat the hanger on the top right marking.
Bend the hanger until it forms a right angle.
Run the hanger under cool water to lock the bend
Repeat with the bottom right marking.
Heat the hanger slowly and apply slow even pressure or it will snap.
Step 4: Bend the second side
Bend the second side like the first.
Step 6: Test fit
The hanger will probably be a litte wider then the bladder. You should be able to squeeze the hanger until it pops into the bladder.
Note the clothspin for holding the mouth valve open.