Which sports require you to weigh in as well as weigh out before and after the event?

Horse racing is the only sport that requires an athlete's weight check (combined with tack weight) after the event.

"Weight cutting is the practice of rapid weight loss prior to a sporting competition. It most frequently happens in order to qualify for a lower weight class (usually in combat sports, where weight is a significant advantage) or in sports where it is advantageous to weigh as little as possible (most notably equestrian sports)."
https://en.wikipedia.org/wiki/Weight_cutting

Formula 1 drivers are also weighed before and after races, usually in conjunction with their car being weighed.

https://www.formula1.com/en/championship/inside-f1/rules-regs/Scrutineering_and_weighing.html

This also happens in cycling events.

velonews.competitor.com/2013/07/tour-de-france/froome-contador-others-targeted-for-bike-weight-checks-at-alpe-dhuez_295850 webpage no longer exists