need (something) (about) as much a fish needs a bicycle
To have absolutely no need or use for something. (Adapted from a feminist slogan coined by Irina Dunn: "A woman needs a man like a fish needs a bicycle.") I'm perfectly happy having a phone that just makes phone calls—I need a fancy smartphone about as much as a fish needs a bicycle. We have enough problems with the business as it is, so we need an audit right now as much as a fish needs a bicycle.