The phrase "flip flop" is commonly used to describe a sudden change in opinion or decision. It means someone was thinking one way and then quickly changes their mind to think the opposite. Full definition
I pretty much lived in flip flops for my entire pregnancy because it was the only thing that would fit on my poor, fat feet. (thefashionablehousewife.com)
The picture was of a pair of flip flops on the sand. (bookbuzzr.com)
No sweaters during Fall is like wearing flip flops in the snow. (thejoifullife.com)