How can I rehydrate a dried navel orange?
Nothing I know of will make them juicy to eat on their own. Likely they were under-watered or picked late. 

Can infuse with alcohol -inject or marinate- and have cocktails.

Or find a compote recipe. Peel still good.

I have tried adding a bit a water to cut halves to 'rinse out' more flavor when juicing but it was not worth the effort.