I used the synthetic urine with success. It came in a small squeeze bottle and said to shake and microwave for how ever many seconds. After that I wrapped a handwarmer around it with a rubber band. Nervous as hell I went to give my "sample". I waited for about an hour or so before I was actually called in to give my sample. Once inside the bathroom I took out the small bottle as I started to really piss. (My advice is to actually practice doing this. Don't try it the first time once you're giving the sample.) Squeezed it into the cup, squeezed some into the toilet flushed washed my hands and left.
Dress nice and be polite when you go. Quiet confidence, try not to look nervous. That's what I did. It worked for me. I've heard both things about niacin, I've heard people eating canning wax. All kinds of stuff, all I can do is tell you how I did it.
I've heard of a lady failing a test and asking if "Testing postive from marijuana is something she could catch sleeping with her husband, because he smokes it."
p.s.
I would still advocate for flushing you system out in the next 25 days and take another home test. We as humans abuse our bodies so much that sometimes having a window to work towards is a helpful thing.