That title may not be accurate Quickest fix or laziest fix may be closer to the truth. We are living in a rented house with large, square ceramic tile floors in every room. Some of them were cracked or damaged before we ever moved in. Like this, or in some cases, worse:
What made the crack vanish? Nothing but plain old blackboard chalk, rubbed into the damaged area, with the excess on the surface wiped off afterward. Sure, it isn't actually repaired, but if someone was coming over, five minutes would make it disappear unless the visitor was actually lying on the floor with their face less than an inch from the spot. Chalk has worked on other surfaces to wholly disguise a small flaw and has the advantage of being cheap, easy and non-toxic. What's not to love?
I hope your week is off to a good start!