How would the conversation even go?
"Sweetie, what are you wearing? 'Cause it smells like ass."See? There's no tactful way to address this issue. I would rather end the relationship than initiate this conversation. I need a tutorial for this. I would pay up to $3 to learn how I can bring this up gracefully. I have Paypal. I'm good for it.
"So, I've been thinking about how you smell and I've decided that I don't like it."
"Did a homeless man pass out on your shirt? Because it kinda smells like one did."