My grout in the bathroom was looking kind of icky, so I started looking for something that I could make here at home to get it clean. The easiest, and seemingly most effective recipe called for just two ingredients: vinegar and dish soap. I was skeptical, but decided to give it a shot.
I mixed the vinegar and dish soap in a squirt bottle in equal parts. The recipe online said to use a spray bottle, but I didn't have one on hand. the squirt bottle worked just fine for me. Just apply to the grout lines. If you are working on a large floor, divide it up into smaller sections. Let the solution sit and soak for a few minutes.
I used an old towel to wipe up some of the excess solution before I started scrubbing. Even without scrubbing yet, I got this much dirt off my floor. Mind you, I had already swept and mopped before I began.
Using a wet scrub brush I scrubbed all of the grout lines. Didn't take a ton, but I did need to use a little elbow grease. I then dampened another towel and used it to wipe up all the stuff I had just scrubbed up. This towel shows how much more stuff came up after scrubbing.
It may not be perfect, but there is a huge improvement over what it looked like before. Now I just need to do the same to the tile on the landing... Maybe another day!