Rehydrating for a comp

I was supposed to weigh in the day before, which would have been perfect, but I can't do it anymore, so I'm forced to weigh in on the same day. I've done it before and it was fine. Last time, I was the first match, so I didn't have much time to rehydrate and eat. This time, weigh-in is at about 9 in the morning, and my match is around 4 in the afternoon.

I usually drink 1 isotonic drink (Iso sport). And just eat whatever, but not too much. What should I eat?