anatomy scan

hi i have an anatomy scan tomorrow and i was wondering if it would be a bad idea to have a milkshake before hand… i know that sounds like a dumb question but i don’t want the baby to move around too much and get hyper making it difficult to scan each part of the body. i also want to know the gender and don’t want the baby to be stubborn lol :( also do i need a full bladder for this appointment?? bc they didn’t say, thank you!