Clean grubby grout with a nontoxic cleanser. Mix 1 cup of dish soap and 1 cup of heated white vinegar then pour into a spray bottle. Shake it well, then spray lightly and let it sit for a few minutes. Scrub the grout with a brush—it'll take a little bit of elbow grease—and wipe up with a wet cloth. When you're done, rinse away any residue with plain hot water.