A woman named Lucy does what are described as "half a dozen provocative squats". She is seen topless while wearing panties. The scene starts in the shower and then she does a dance routing while continuing to be topless. It's more of a humourous scene. It could even be called artistic, but it's certainly not intended to be sexual.
While the nun "tries to OD", Janet and Lucy notice a pervert "beating off" nearby. Lucy considers this "exciting" and grabs one breast while clearly aroused. Lucy is topless at this point while Janet is struggling to get a corset-type piece of clothing on. Only Lucy gets aroused. The scene is mainly played for laughs (like much of the film).
While not visual, there are several lyrical references to sexual acts throughout the film (and soundtrack). IE: Lonesome Cowboy Burt wants a waitress to "sit on his face" and Howard wants to "go to the club or the bar or wherever the pussy is found in the town that your band is booked to play in". Songs like "Penis Dimension" and "What Will This Morning Bring Me This Evening?" are about sex, but normally in a joking way.