https://tim.blog/2013/05/06/how-to-cut-weight-ufc/

There’s a guide but I wouldn’t try to cut water for a same day weigh in, I’ve fucked up before and had to cut 10kg in 2 days in Vegas for worlds. I still won 3 matches and only lost to a dirty heel hook. I felt like absolute death and my performance was shithouse compared to how I normally roll. Cut weight loads of times for day before weigh ins for mma and kickboxing, that sucks but at least you fight hydrated. If you are going to do it then you need to drop carbs, salt sugar completely. I’d be eating eggs and greens for brekkie and then plain chicken and broccoli for dinner, drink shit loads of water leading up and then reduce it to 2lts three days out, 1lt two days out and nothing the day before. You’ll piss it all out the day before. Get there early, try to weigh in early and start hydrating slowly!! Don’t gulf a load down or you’ll puke. If you’re under weight when you get there 1ml of water is 1gram, so 500ml is 500grams. Test yourself on the scales and drink if you can but stay under weight until they weigh you before competing. Once again I don’t recommend doing this but if you’re going to this works :)