He had been thirsty, sort of, so he ate the ice cream in the fridge. If he had known it was lemon he would not have bothered. He ate the ice cream voraciously initially, and he briefly felt better. Any feeling of satiety was quickly overshadowed by returning thirst. The ice cream dried his lips and tongue, compelling him to eat more.
The lemon flavor caused him to pucker as he continued eating. It felt as though the water was being squeezed out of his mouth, making him increasingly uncomfortable. His lips became dry and eating the ice cream uncomfortable.