There’s been a few studies on this, and most of the supposed remedies have been found to be little or no more effective than just rinsing with water or saline.

That said, in theory, I feel like baby shampoo is probably a pretty good bet, it makes sense on paper. Most pepper sprays are oil-based, soap/shampoo is a surfactant so it helps to rinse out those oily substances with water, and baby shampoo in particular is non-irritating to the eyes.

There’s a few purpose-made products for this, I’ve seen a few recommendations for sudecon wipes from first-responder types. I have no recommendations about how to best get your hands on those sorts of products in case you’re worried about leaving a paper trail.

For my own personal kit (that I just try to keep well-stacked for any eventuality, I have pepper spray on my dog’s leash so I figured I should know what to do if I even accidentally mace myself) I’ve settled on sterile saline eye wash and baby shampoo. Haven’t had to use it yet, so I can’t attest to the effectiveness, but I figure it’s gotta be better than nothing

And it makes enough sense on paper that I figure if nothing else maybe I’ll be able to placebo effect myself into believing it did something.