GTT test

I was told to come early for the first blood test after fasting the night before (10pm) and then drink the sweetened beverage and wait for 2hrs to get my blood drawn again. Can i drink a little bit of plain water while waiting?

I asked the nurses and I had different answers. One said that it’s okay but just a few sips and the other said no. I took a sip earlier cos i was feeling a bit thirsty so i was wondering will that affect the result or something? 🤔