If it is M&P it needs to packaged airtight in a nonporous substance.
The sweating is the glycerin pulling moisture out of the air & binding it to the surface of the bar.
I find it best to wrap it tightly in saran wrap first, then if you want to place it in a pretty box, wrap it in gift wrap, drop it into a clear bag to tie w/ a bow or etc, you can. The saran keeps it airtight to prevent shrinkage or sweating.