Bunnies are self-groomers like cats and should never be bathed. Its unnatural and stressful -which can cause them to go into shock and even die.
If very dirty, use a damp cloth, or do a bunny butt wash. Many shops often sell bunny shampoo and related products - the only way we can vote against them is not to buy them and to educate others not to buy them. We really want to discourage people from bathing their rabbits.
Even if you do find a bunny that tolerates it, it’s still stressful and not necessary. If your rabbit does get wet for any reason, be sure to dry him properly.