Giving 3 month old soda and candy...

How do I make my dad stop? He shoved a sour patch kid in her mouth and I pushed it away as fast as I could but she got some of the sour stuff. Then he tried to give her Dr Pepper and I had to shove his hand away 3 times!! She hasn’t even had baby food yet.. only breastmilk and I had to quit eating dairy because she allergic. What if he gives her something and she has a bad allergic reaction? I told him it’s not safe and that she hasn’t even had baby food yet soda and candy is not okay but he just told me people use to do it all the time and just keeps trying. Even when she’s older I don’t want her eating unhealthy stuff. I can’t even trust them to babysit now. What do I do? He won’t listen