When an item you use regularly is on sale, stock up. That way you won't have to make trips to the store for just one item and have to buy it when it's out of stock at home. Just be sure to look at expiration dates. Only buy what you will use before it goes bad or you're throwing money away.
For example, I purchased a year's worth of loofahs when they were on sale, and now I'm making sure to change them out regularly (because of bacterial buildup that occurs over time) for substantially less! It's healthy as well as frugal!