It is a top comment from this youtube video. I'm sure it is a way of expressing sense of humor, but I just can't get it. My guess is that they are just saying the video is just as short as the time it takes to make a sandwich.
The comment refers to the poor video quality (240p).
However, the joke most commonly used potato instead of sandwich.
More on this joke: http://knowyourmeme.com/memes/recorded-with-a-potato
I'd say he is either referring to the poor video quality or just trying to create humor out of randomness. In my opinion it is probably the latter.