The reason these sisters sell fruit-flavored drinks is just as sweet as their ingredients

"Stay in the mix with a fruity fix" is a phrase these young entrepreneurs live by.

Armani, 13, and Amaya Jefferson, 12, founders of Mani & Maya's Fruity Treats, started their own business in Summerville, South Carolina, to raise money to help find a cure for sickle cell anemia, which affects their 1-year-old sister, Taylor.

Taylor was born with sickle beta thalassemia, a blood disorder that affects the production of hemoglobin.

"Seeing our sister getting hospitalized a lot, we wanted to help raise money for other people that have sickle, like Taylor, and help find a cure through sickle cell research," Armani told "Good Morning America."

To do so, the Jefferson sisters sell pink and strawberry lemonade with fresh fruit inside. These drinks come in 16-ounce, half-gallon and gallon-sized portions. They also offer a fruit boat -- an assortment of fruit such as strawberries, kiwis, pineapples, blueberries, blackberries and sometimes lemon, mixed with yogurt inside a pineapple -- and nutritious fruit smoothies with similar ingredients.

And you do not have to be in South Carolina to get these sips, as they can be shipped right to your door.

"We do next-day shipping. When we do ship, it comes in a styrofoam cooler box, and we include cold packs to keep it cold," said their mother, Desiree Hamilton.

These middle schoolers are not only excelling with their business. Both attend Gregg Middle School, where Armani's favorite subject is math and Amaya's is reading. Armani and Amaya were also selected to join the National Beta Club, an organization that supports rising leaders.

And they showcased their leadership skills in April during their first Kid Entrepreneurs Expo, giving children like themselves a chance to market their businesses. It was a sold-out event with 14 kid vendors and sponsors who were happy to help. With more than 300 attendees, guests were able to enjoy free food, face painting, a panel discussion from experts and even a live performance.

"Because of this event, we were able to donate $500 to Medical University of South Carolina Children's Hospital, which is where our little sister Taylor is seen for her blood disease," Armani said.

The girls sell their lemonade every weekend either in front of their home or their grandparents' home. And they've partnered with Nana's Seafood and Soul restaurant, located in downtown Charleston, which sells Mani & Maya's Fruity Treats that they deliver each week.

"We enjoy making our treats because we have a lot of sister-bonding time," Amaya told "GMA."

Taylor is a strong little warrior and has not been hospitalized since February -- and was also the special guest at the Kid Entrepreneurs Expo.

"It makes me feel proud and it is good to help people in need and waking up knowing I am helping change the world," Amaya said.

Mani & Maya's Fruity Treats also celebrated its one-year anniversary this month. How did they celebrate? By continuing to serve lemonade for their little sister.

"Knowing that we are so young and knowing that we are doing something so great, it feels amazing. You do not see many kids at 12 and 13 making a difference like this," Armani added.

So far, the sisters have donated more than $800 and plan to keep working hard until a cure is found. Expanding their business by possibly starting a clothing line is also on their minds, as they plan to continue donating funds to MUSC Children's Health.

"This makes me feel really, really proud," their mother said. "They did it, and this is their business."