If you can get around the temp problem of the sample and having to urinate in front of someone, fake urine can be made with distilled water, a dash of salt and a drop of food coloring.The only question a lab tech might have is if it looks like water.If it does they will check to specific gravity.The salt will take care of that.This is all thats done before putting the sample thru which ever type of tests to be run.And it will be negitive .