I'm going to call bs on this one.
Although here's what could be happening...Take water, put some clorox in there just so that bacterial/mold/stuff/funk wont start to grow, then cut a hole in your roof. Glue bottle up in the roof so that light can pass through.
Next, while recording footage of said light, overexpose the shot so that they appear to be putting out a ton of light. Make sure to only film on bright sunny days.
In all seriousness, you can get those sun tube skylights that will look that bright easily. We had them installed at my old job, and they lit a huge warehouse for free, with beautiful daylight. Looked very similar to the quality of light in this video.