The new bladders (for several years now) are made of a material the inhibits growth of the bad stuff. It has been a very long time that I have had to do any cleaning on one.

I put Gatorade or water in mine. After use, I rinse the bladder & tube with warm water, then fill it half full with (Gatorade or water), blow through the bite valve to fill the other half with air and then lay it on it's back in the freezer. When I am ready to use it, run the cap under warm water until you can open it, fill it the rest of the way up with Gatorade or water. You then have cold drink for a very long while.

If you fill the entire bladder with Gatorade and freeze it, then the stuff that melts first is very strong and the last stuff is mostly water. With half frozen and half liquid, the taste if pretty good the entire volume.

Before the new bladders and cleaning kits, I took a wire hanger that had a plastic coating on it and reshaped it to hold the bladder open the same as the drying kit device.