Grandma gave my newborn apple juice and water 😥

She was baby sitting he's only 4 weeks she said he had 3oz of water and apple juice and he loved it WHY WOULD SHE DO THIS I TOLD HER JUST FORMULA. I'm so mad she won't be baby sitting for a long time I had only gone shopping and was a couple hours maybe 3 my baby going to be okay? I thought I could trust her she said I loved it as a baby too so that's why she let him have it 😓