Kids don't need a complicated diet, just fewer processed extras and more of the plain stuff. A useful starting point is the plate itself: roughly half vegetables or fruit, a quarter a protein source (egg, chicken, beans, fish), and a quarter a whole grain like brown rice or wholemeal bread. It's not a rule to enforce at every meal — it's a rough shape to aim for across a day.
Breakfast is where a lot of the added sugar sneaks in. Flavoured cereals and sweetened yoghurt drinks can carry more sugar per serving than a slice of cake. Plain oats with sliced banana, or wholemeal toast with a boiled egg, gets a kid through the morning without the mid-morning crash that a sugary cereal tends to cause.
Snacks are where parents have the easiest room to swap something out. Instead of biscuits or chips, a small box with cut fruit, a few age-appropriate nuts, and two or three Kurma Rabbi dates covers the sweet craving and adds real fibre and potassium at the same time. Dates work well here because they're naturally sweet without added sugar, and they keep in a school bag without refrigeration. Whole nuts are a choking risk under about age five — chop or grind them for younger kids.
Water should be the default drink. Juice, even "100% juice", is mostly sugar and water with the fibre stripped out — a whole piece of fruit is the better version of the same thing. Milk is fine alongside meals; it doesn't need to be flavoured to be worth drinking.
Getting kids to actually eat vegetables usually comes down to repeated, low-pressure exposure rather than persuasion. A food offered again and again without a fuss — ten times, sometimes more — tends to get accepted far more often than a food pushed hard once and dropped after the first refusal. Keep the vegetable on the plate even on the days it comes back untouched.
None of this needs to be perfect. A packet of chips at a birthday party or a sweet treat on a Friday isn't a failure — it's what a normal diet with room in it looks like. Consistency across most days matters more than strictness on any single one.