If you look at all their pictures of their tortoises as adults they are as smooth as can be and the pictures of the babies look good too. It also shows the enclosure that he keeps them in.
Just though of this there is clear Gatorade that you can use that wouldn't have artificial coloring, and I didn't mention if it does turn out to be ok to do, I would also mix it with mostly water.
Maybe them drinking it would good for them but if you soak them in it then you would have to soak them in water afterwards to clean them off or else they would be all red or blue. Also I wouldn't do this every day though maybe once a week because all living things need water, and a daily basis...