When you are banging a chic doggie style then apply a small amount of hot sauce to your thumb. Then your proceed by sticking your thumb in her anus. She will jump, flip her over then feed it to her.
On the morning after, when you have sex with the still-sleeping girl next to you before she fully wakes up to realize what is happening then hurriedly leave her place.
"Wait, I thought you only had sex with Emily last night?"
"No, dude, I gave her a Mexican breakfast this morning and bolted before she even knew what happened!"