I have dyed red hair and I admit I was hesitant to use this method at first because I feared for the dye in my hair. As you can see by photo #2, I have AMAZING hair (I'm also modest) and it's shiny, bright red and healthy.
Get one of those plastic bicarb containers to start. I reuse this one a lot, using that cheap $.90AUD a bag bicarb/baking soda and refill it when it goes empty.
Combine Apple Cider Vinegar (or regular vinegar) 1 part vinegar, 4 parts water and shake to combine. I use an old Palmolive bottle because it has the perfect stream for getting your head. One bottle full should last 4 washings of super long hair like mine and two of men's hair... because my husband washes his hair pretty much never.
Go to the shower!
First get a handful of bicarb into your hand and work it into your hair. Scrub a dub dub as much of it as you can. Rinse with water.
Next, use the vinegar as conditioner. Use about 1/4 of the bottle to really get all that bicarb out of your hair. It should also work as a mild detangling agent, but will not feel like actual conditioner - because actual conditioner builds up on your hair to make it gross.
Because I do not want to be arrested for taking shower photos of myself on a site with minors, here is a picture of a kitten.
Let dry naturally and TRUST ME the vinegar smell WILL dry out.
Then your hair should look like this! That is, if it's red, long, done up on the sides and you're me. Otherwise, your hair should just look like your hair, only healthier and happier.
And you just saved thousands of dollars a year.