Don't buy a full-sized version when you want to try a new product. Get a free sample.
How? There are lots of websites that promise free samples. One that I know is safe and reliable is Walmart.com. There's a link for "free samples" right on their home page--and they offer lots of samples, and the offers change frequently. Currently, as I write this, you can get free samples of Pull-Ups, toilet paper, baby formula, two kinds of shampoo, doggie treats, and other products. Try it before you buy it.
Another way to get free samples (or coupons for heavily discounted products) is to go to the company's website. They often have promotional offers listed there. If not, click on the "comments" or "contact us" button--many sites allow you to fill in a form and make a comment/complaint about a product, and they often (but not always) reward your efforts with free samples/discount coupons.