(Assuming, of course, that men had women's bodies.)
Ultra mega super absorbent tampons, for those manly flow days.
Support bras would tout suspension inspired by bridge engineering, to keep "the bitches" on prominent display.
No change in sports bras except the addition of prosthetic "it's cold outside" nipples so guys could show pokies without actually rubbing their nipples to bleeding while running.
Breast implants would only come in DD or larger.
The small sex toys would be 8 inches long and 3 inches thick.
"Male hygiene" products would have names like Cootch-Douche, and SprUnt (pour one out for George Carlin).
There would be no jumping on trampolines in white clothes. The lead-in for tampon commercials would look like the elevator doors opening in The Shining.
And if only men bred men, birth would look like this. (NSFW, but the true payoff for this comic is on the moderately safe next page. No father could be more proud.)