Unfortunately, this is a subject I am well versed on, learning the hard way in my early monger years. Early morning visits are best if you are going to risk house slippers. Some places like spa 27 have Lysol spray you can douse the slippers with if you want to give that a try. The best thing you can do is bring your own sandals. If you go to the gym, having a gym bag makes everything easier. You have all of the products you need to come home smelling the way you left. Just remember if you go later in the day, you should “hit the gym” on the way home, otherwise your freshly showered self is a dead giveaway.
Also remember, that if you are going to introduce a gym bag into your routine, it has to be part of a long game involving more gym usage or sign up. This has to be introduced over time as major routine changes give even trusting SOs pause. Guys get caught all the time because they don’t know how to be subtle…don’t be that guy. Good Luck!