Actually, freshwater dips work for corals, especially LPS with thicker tissue, but also for SPS.
I did once an accidental (mixed up the rinsing and the recovery container) and way too long FW dip with some corals and 3 out of 5 made it through and are still with me months later: an Acan, a kind of Montipora with thicker tissue and another SPS that looks a bit like an Acropora but isn't one. A bonsai Acropora and a scrolling Montipora didn't make it.
I also know that many German reefer do FW dips against coral pests. You just need to keep it short and not soak them for half an hour like I did