A cold plunge when you’re either still drunk or hungover is a cure all.Closest I've got to one is doing the New Year day dip at Withernsea. Did it for about 5 consecutive years. The worst thing about it was getting out the sea and standing on the sand bloody feet like blocks of ice. Best thing was your hangover disappears in seconds.
My brothers stag many years ago in London, we were hammered, went to a sauna in the early hours and did alternate hot and cold, finishing cold. Came out sober then went straight back on it in Smithfield at about 4.30 in the morning. Market pubs are gods gift to the 24 hour clock.