what food does helen keller love to eat?

Helen enjoys eating candies, which everyone in her family gives her (probably because they feel bad for her and want a way to communicate their love for her). Since she is blind and deaf, she cannot easily communicate or understand what is happening around her.
Before Annie Sullivan arrives to teach Helen, several members of the household give Helen sweet treats, not realizing that others have already given her treats. First, her mother (Kate) gives her a peppermint drop. She says,

"I don't think one peppermint drop will spoil your supper."

Soon later, Viney, their servant, gets Helen a tea-cake. She thinks aloud,

"Guess one little tea-cake ain't [going to] ruin your appetite."

Moments later, Helen's father is talking with her. He hands her a large stick candy, saying,

"Here. I brought you some stick candy, one nibble of sweets can't do you any harm."

Within moments, Viney calls out to him, reprimanding him for filling her up with "that trash" before her dinner.
Overall, the family loves Helen, and everyone wants her to be happy. They find ways, such as giving her sweets, to show their concern for her. However, giving her so many treats causes her to think she can have whatever she wants. Most members of the household begin to give into Helen's every wish whenever she gets upset. Her stubborn behavior, caused by spoiling her with everything she wishes for, is part of what Annie Sullivan seeks to fix while teaching Helen.