How Do You Childproof Sliding Closet Doors That Are All Mirror?

I would get a wooden dowl that you can put down on the floor like you put in windows or sliding glass doors to keep them from being opened from the outside. You can have them cut to fit pretty snugly so that your little one can't roll them or remove them.
Dowls come in varying circumfrences and are inexpensive.
I would try that.

Best wishes.

I love refrigerator locks for everything that you can's drill into. You need two clean and smooth surfaces for them to stick onto. Not pretty, but no way a toddler gets them open. $5 at Target.
I have had them on our wooden kitchen cabinet doors and the stove door and they came off clean when we were done.
http://www.safety1st.com/usa/eng/Products/Home-Safety/Lat...
Good luck!

Dowels might work but maybe not since mirrored doors tend to be not as thick as wooden ones. I loked up on a website and got this:
http://www.safebeginnings.com/WebComponents/Catalog/Publi...
You can put this on the mirrored door and when time comes to remove it, use a razor blade to peel carefully if it does not comes off well.

I am not sure if there is a product that is actually made for that - but the first thing that comes to my mind is a shower curtain rod that is spring loaded - and you can stick it in between the doors and the wall to keep it from opening. I guess you would have to get one for both sides, but you could put it up high enough that your child would not be able to reach it or hang on it and the doors would not be able to slide......