The Freebie (2010)

Annie and Darren have been married for seven years, and they love each other as much as the day they were wed; they're affectionate, have fun together, and enjoy games such as crossword puzzle races. They would seem to have a perfect relationship, except for one thing -- they haven't had sex in ages, and seem to have lost all interest in making love with one another, no matter how they try to put each other in the mood. Hoping to put some adventure back into their lives, Annie and Darren come up with an unusual idea -- they each get one night in which they're free to find someone and have sex with them, scot-free. But is this going to help their relationship, or is it just going to turn a small problem into a big problem?

Source: TMDb