Heads up this is from 2015. Not sure if reflective of what would happen today, if there is any difference in viewership.
Here is a blog post from Candy Japan from 2 days ago, about experimenting with youtube giveaways: http://www.candyjapan.com/youtube-marketing-horror-story
0 sales.
Given it would be close to impossible to notice a lift from that viewership, I'd suggest this 'test' failed more from being too small.
Edit: removed redundant word.