Ironically, hump day is the day of the week Americans are least likely to buy condoms. According to data from on-demand groceries company Instacart, condom purchases bulge on the weekend, and shrink to their lowest point by Wednesday. (To be fair, Instacart shoppers buy less of almost everything on Wednesday.)
If instead of looking at totals, we examine the proportion of all items bought that were condoms, Monday is clearly the least sexy day of the week.
(Thank you to Owen Phillips for the stimulating insight.)