I went on the best sober vacation. It was not technically deemed that but if you got blasted every night you would not have been able to fully enjoy it. It was surf camp in Hawaii. Out of the six other travelers there, one was in recovery. It was so helpful to my sobriety. I think wellness retreats in general where you do sports and challenge yourself will lean towards alcohol-free. Of course you might not get a completely sober environment (I think one night a couple of girls drank at dinner) but you will get an environment much more conducive to sobriety and maybe more importantly recovery.
There are surf camps in Hawaii, Costa Rica and Mexico. Other ideas would be yoga retreats or mountain climbing or hiking adventures. And most spas don't allow alcohol...