How to get a successful 3d scan?

Hi ladies. I went to get my 3d (optional) scan today. Unfortunately baby was not cooperating. He had his hands in front of his face and the technician said he was sleeping. No matter what we did he would not move lol (stubborn like daddy!)
So the lady was nice enough to offer me to come back at no extra charge in the morning. Is there anything I can do to help me get a good scan?  Anything to eat or drink or not eat or drink? I really only wanted to do one 3d scan during my pregnancy but unfortunately I have to do two now. Any advice would be appreciated 😊