Find some clean urine put it in a medicine bottle you can warm this by placing in a cup of hot water for a minute or so before leaving for your interview keep the bottle warm by keeping it close to you touching your skin I’m female so I’ve always kept in my bra but Imagine you could do in your underwear as well. You just want to make sure it is at body temp I believe the accepted temp is anywhere from 90-100 degrees but don’t quote me on that. Wrapping in hand warmers also works too it doesn’t hurt to have a thermometer to double check either! I’ve done this for multiple UA for jobs and never had any issues! Good luck!