My experience is such that keeping young sulcatas in high humidity environments can become very dangerous should they receive a sudden chill or should mold develop in said environments. The simplest way to ensure a hatchling's hydration is to allow for an environment that provides areas of relative humidity, which translates quite simply as excavatable substrate. Allow your young tortoise burrowing capability, and they will create their own humid environment, just as they would in the wild. This is the best option, in my opinion.

T.G.