Best way I know to rejuvenate a lead acid battery is to shred it, melt the lead down, and make a new one. That's where your core return goes and how new batteries end up on the shelf.
The only "success" I've personally had making a weak battery work longer is by popping the caps (this won't work on a sealed battery) making sure the fluid level is at least covering the plates, add water if needed but just enough to cover the plates (level goes up with more charge). Then I roll a big, dumb, manual charger out and overvolt the battery ( I think around 18V) with the max rate/"boost" tap on the transformer to balance the shit out of it for like half an hour. Then I top the water off properly and that will sometimes keep it limping along for another month or two. This is a dangerous trick as the battery spews hydrogen, no smoking, make sure connections are secure before applying power, and stay away from the thing just to be safe, internal faults can also be an ignition source. I really don't recommend anybody does this, the risk/reward simply doesn't work out.
As mentioned by Gyro, you really need to know what you're doing to charge batteries with a bench supply, and not smoke said bench supply. They usually have little to no protection against using the output as an input, unlike an actual battery charger.