Mix a half cup of baking soda, 1/4 cup hydrogen peroxide, and 1 tsp of dish soap. Apply to grout and let it work for 15-20 minutes. Scrub with an old toothbrush and rinse.
Sprinkle baking soda on a sponge and scrub the grout. Then spray lightly with vinegar. Let it sit and scrub and rinse.
try this one: https://www.craftylittlegnome.com/the-best-homemade-grout-cleaner/
Hi, Joe - I have an easy and cheap recipe here to try: https://thehowtohome.com/diy-eco-friendly-and-money-saving-scrubbing-cleanser/
Here is a good video to watch for this, https://www.youtube.com/watch?v=orJVJKfPovE
Hope it helps!