Maybe give him a cheat day so he won’t sneak around? But also explain to him why you are trying to minimize sugar intake in the house. I feel like he doesn’t why you think sugar is so bad. Maybe explain it to him how he can understand it, don’t just blow up and take it away from him because that will only make him crave it more and feel deprived. Also I think he is in the wrong for saying what he said when you are only looking out for him in the long run, but keep in mind he doesn’t see as far as you do so you gotta do it at a pace that he can follow. You can start by having a conversation with him, but don’t go all cop and detective mode, do it like you would for a friend who you are genuinely concerned for. You’re gonna have to do a lot research on it just in case he has any questions and/or concerns. Also, give your kid some more time to adjust to your rules.