You don't say why you want to clean the rim. Cleaning rims is only necessary for cosmetic purposes.
Unless carbon, there's very little you could possibly use that would damage it, unless you're into strong caustic drain cleaner kind of stuff. As others have said, warm water/detergent is a good way to go.
If it's for braking performance and/or rim wear, the brake blocks are what you need to concentrate on, not the rim. They can get swarf/ other crap embedded in them which can have a radical detriment to braking power and rapidly wear through rims. Take a close look at them, remove anything embedded and if in any doubt replace.