Spartan men were avid practitioners of dude-love. While we might be tempted to think this made them champions of gay rights, the reality was that women were so poorly regarded in ancient Greece that, not only weren't they regarded as citizens, they didn't even deserve your warm pork injection.
The problem was that when the time came to do their duty to their species, Spartan men didn't even know where to stick their bits. So to facilitate the soldier's transition from gay love to straight love, brides shaved away their femininity and threw on some man clothes.
As for the sneaking around stuff, Spartan men were required to live in military barracks until the age of 30, but the average age of marriage for men was 25. So most couples married, did the hanky-panky in the woods or whatever, made some babies, and didn't even live in the same household for the first few years of their marriages. Hey, we wonder how the Spartan men comforted each other over the absence of the women in their lives? Eh, we'll probably never know.