I didnt!They told me to drink the litre etc but i couldnt either so i didnt,interestingly my sister went for a scan the week before with some gyno problems and she told her its nonsense just drink a bit so she barely drunk a glass and they said nothing,then i went and decided to try to drink 500mls but on the way i couldnt wait so i let it all out and so i had a bottle of water on me and honestly had like 3 big gulps before i went in so i had had something and the lady never said anything,i think its because there is enough fluid now,dont worry i didnt!