The science
Do electrolytes actually help with hangovers? Alcohol makes you pee out more fluid than the same volume of water would. A study that had healthy men drink beer instead of water tracked urine output and blood markers over twelve hours, and found significantly higher fluid loss in every beer condition, along with signs of more sodium lost along with it. The effect showed up early and then partly reversed later in the session, but the net loss was still measurably higher than plain water drinking (PubMed, Sailer et al., American Journal of Physiology).
So what
This is why a big night out leaves you drier than the number of drinks alone would suggest. Replacing the wine or the six beers isn’t enough, your kidneys pushed out extra fluid too, because alcohol briefly switches off the hormone that normally tells your body to hold onto water. That’s a purely mechanical effect, it happens whether you’re a seasoned drinker or someone who had two glasses of wine at a work thing. Day two of a hangover, the headache, the flat mood, the fog that makes your 9am meeting feel hostile, overlaps a lot with plain dehydration symptoms, on top of whatever else alcohol itself is doing to you overnight.
Bottom line
Electrolytes won’t cure a hangover on their own, and they don’t actually help with hangovers by speeding up how fast your liver processes alcohol. But if part of how rough you feel the next morning comes down to fluid and sodium loss, replacing that is a reasonable, unglamorous thing to do before bed or first thing when you wake up. It’s not a fix. It’s just addressing one piece of a bad morning that actually has decent evidence behind it, rather than guessing.