I have given baths occasionally when needed. I usually fill the sink with an inch or two of water and use my hand or a small cup to rinse over the necessary areas. Mild hand soaps have worked fine for me, I just lather in a tiny amount and then rinse again.
The important thing to remember is to make sure that any soap you use is rinsed thoroughly because they WILL groom themselves after and shouldn't be ingesting soap. And then towel dry first and keep them in the house in a warm area until they're fully dry.
You know your rabbit. Go slowly and if he seems stressed, obviously rinse him and end the bath there. But in general, mine have been unphased by the bath itself. It's just making sure the fur is rinsed thoroughly and dried fully before returning them to outdoor areas (if that's where they live).
I'm certainly not recommending baths as a regular thing, but I've been able to do it occasionally when needed.