There is lot's of technical proof that 'electronic de-sulfation' does in fact work, but........
I've studied the technology extensively, I actually now build my own units (NO, don't ask me to sell you one) and have done extensive testing using a base of acquired marine batteries. What I will offer:
connections matter - keep the leads as short as possible using fairly large gauge wire (mine are actually made to sit on top of the battery with the leads only long enough to reach the terminals)
a small charger/maintainer is required - the de-sulfator generally gets it's power from the DUT (device under test) (I don't pay a lot of attention to what I use for a charger, anywhere from a 'tender to a 15A auto unit
the quality of the components and the circuit design of the de-sulfator matters - I've tested some I built w/ cheap components as I developed my circuit, I found a few key components that I spend a top $$ to get quality
generally, if a battery is sulfated, it will show an open terminal voltage near it's rated, but when you attach a old style manual charger it won't take a charge or a new auto style will error showing 'bad battery' or such. These are candidates for electronic de-sulfation. I'll document it's open terminal voltage, attach my device, and a charger, and make sure it's got water. I leave it for 30 days or so, detach the charger and device, let it set for a few hours and compare the open terminal voltage to original reading. If it's in the range of > 12.6V, I'll then do a load test w/ a 50A load and see what the terminal voltage drops to. This will identify if there is a cell that is bad, if so it will drop a bit, then drop dramatically about 2 volts, then continue dropping as it's loaded. Usually, removing the load will return back to somewhere near 12V, but I usually don't continue w/ that battery as the bad cell will likely never recover. If the load test simply drops continuously, I then apply a smaller continuous load to discharge it down to about slightly below 11.5V, then reattach the device and charger and leave be for another 30 days. Another quick load test will verify if it is serviceable, if so I put into service keeping a de-sulfator device on it 100% of the time. (I always keep some kind of maintainer or charger on my marine batteries if there's a device on top)
My particular de-sulfator device delivers about (varies dependant on state of battery) a min 50V pulse to as much as 150V for about 3 microseconds every millisecond. You can actually here it 'sing' when it's working, about a 1Khz tone emitted from the coils inside it.
I've also tried some of the eBay junk, it's that - junk, I've not found one that works, and I've used some of the commercial ones, I've a couple auto-chargers w/ de-sulfate modes and a battery-minder that work OK, but I went my DIY route for a couple reasons, I'm electronic engineer by education, and cost - I can build my own better for cheaper, and since I'm putting one on every storage battery I have, I need a lot of them (5 boats w/ multiple cell banks on-board) plus the satisfaction of debunking a myth. I have a couple off-grid acquaintances that also swear by the technology, as they have built their power banks w/ discarded batteries.
just trying to contribute, the technology is SOLID, it's the quality of the implementation that either makes or breaks it's success.
