How did Tom and Ma get Grandpa into the truck even though he didn’t want to go?

They knocked Grampa out with "soothin' sirup", which they used to spike his coffee.

Ma said, "Tom, I got a half bottle soothin' sirup I got for Winfiel' when he had them earaches. Think that might work? Use ta put Winfiel' ta sleep when his earache was bad."