fasting for ultrasound question

hello this is maybe a silly question and an even sillier thing to be concerned about but i have an ultrasound on tuesday to check for gallstones after months of pain, its at 10am and ive been told to fast from 10pm the night before. am i allowed a cup of tea? like with (oat) milk? or is that not fasting? i dont want to mess the scan up but i also want a cup of tea if thats allowed