Tips Look for Sweet Onions that have a light, golden brown colour with thin, papery, pale skins which are easy to peel. They should be relatively firm to touch and avoid buying any that have soft spots or bruises. As Sweet Onions have a higher concentration of water as opposed to solid fibre content, our advice for storing onions - is not to store them but instead buy them as fresh as possible. However to keep them at their best condition, store Sweet Onions in the fridge. This slows down the dehydration of the onion which causes the onion to become stronger and therefore keeps it as mild as possible.