Yes, I have fucked in the toilet before. Really thrilling especially during working hours. Knowing that your colleagues are still working and not too far away. I used to sneak in to my office's Executive Toilet (which is extremely clean since it is basically only used by my Ang Moh boss) with my Ang Moh boss' PA for quickies. Really exciting. Like bro pl666 said, doggy position is the only comfortable position to fuck in the toilet considering the space. But for me, it was all about the thrill.