An eastern Tennessee father and stepmother of a 5-year-old girl who died after being forced to drink large amounts of grape soda and water as a form of punishment have been sentenced to 35 years in prison, authorities said.

Randall Vaughn, 42, and Mary Vaughn, 59, pleaded guilty to second-degree murder and aggravated child neglect and were sentenced on Monday in Rogersville, Tennessee, District Attorney General Dan Armstrong said on Tuesday.

The Vaughns forced the girl, Alexa Linboom, to drink more than half a gallon of grape soda and water over two hours in January 2012 after they found she had consumed a soda or two they had told her were reserved for the adults, Armstrong said.

Armstrong said the consumption of the large amount of liquid caused the girl's brain to swell.

She was taken to a hospital in Johnson City, Tennessee, where she died two days later, authorities said. Rogersville is about 210 miles east of Nashville.

Her four siblings, who are now 7 to 16 years old, provided key details that led to the indictment of the Vaughns in February and would have had to testify at trial if not for their guilty pleas, Armstrong said.

He said the offer of a plea deal was made to ensure that the Vaughns would spend the rest of their lives in prison and to protect the girl's siblings from having to take part in a potentially high-profile trial.

Her siblings are in foster care, authorities said.