By default YouTube won't allow us to watch inappropriate (18+) videos without signing/logging in, you need to log in so that YouTube believes you are 18+ and you are allowed to watch this video without any issue.
But this restriction is pretty annoying when you are in a strange browsing center or if you are watching a video on your not-so-trusted friend's smartphone/laptop. I'm sure you might not like risking your YouTube/Google account details. So is there any way to access that age-restricted YouTube video? There is an easy trick for that.
Search for your desired 18+ video, being a movie freak, I ended up typing "raw movie trailer 18+", and we clicked on the first search result. Since we didn't sign in and it's an 18+ trailer video, YouTube requested us to log in and check the video. But what you can do is, below the YouTube video, go to Embed > Show More and tada, here is your age-restricted YouTube video, you can now watch it even without your YouTube account details. You can easily bypass YouTube's restriction for this video.
This is a pretty easy workaround which most of us won't know, but definitely worth it.