You can do a lot of things, like selling old study or work books on eBay. You could look into having a yard sale and sell old toys, shoes, and clothes. You could have a bake sale or lemonade stand, but to make it stand out, add a twist like blackberry mint lemonade or lemon curd sunshine. If you are creative with it, you can attract more customers.
I personally have enjoyed working a direct sales/home based business on the side. I found a good, legitimate company with very low upfront costs/overhead. It has been a great experience. Just be sure that the company offers training and some sort of simple, step-by-step system and it helps if they are in the DSA Top 100– instantly proves their legitimacy!
It’s sometimes hard to comprehend just how much people love t-shirts. And with the right niche, marketing, and tools, you can create an online t-shirt business that makes you extra money online while you sleep. (Even Bloomberg and Forbes feature stories from entrepreneurs who've done just that.) Services like TeeSpring make it easier than ever to create a t-shirt drop-shipping business where they handle the sales, printing, and shipping, and you’re only responsible for design and marketing. For more tips, check out this simple guide to launching and marketing an online clothing store by my friends over at Selz.
Find a profitable niche. Starting with your interests, write down as many niche ideas as you can. Think about topics people might search online. Ideas include passions (like surfing or body building), fears (like spiders or speaking in front of crowds) and problems (like getting out of debt). Do keyword research to see it others are interested in the topic. Find out if a domain name is available that matches the keyword 100 percent. 
While this isn’t exactly a long-term solution for making money (since you have to pay it back), it is a reliable way to get some extra cash when you’re in a pinch. It’s also a great way to make money by saving money if you use a personal loan to pay off high-interest debt, such as credit cards. Since getting a loan is one of the easiest ways to make extra money, we felt we had to include it.
Donating plasma can actually work out better than selling your blood. It takes longer to donate plasma because they will put your red blood cells back in your system. The upside is that you can donate plasma as much as twice a week and you can make anywhere from $40-$60 per donation. You can make that $100 in less than a week if you can stomach the needle.