From the movie Fifty Shades of Grey (2015)

“I’ll be wearing a burlap sack.” – Quote meaning

As they’re suppose to be discussing their “relationship” contract, Ana doesn’t want Christian to be distracted by anything that she’ll be wearing. She wants to be taken seriously, so she jokingly says she’ll be wearing burlap sack as to not appear sexy. Christian will be forced to focus on what she has to say, not what she looks like.