There is no diet or special plan that you can do.
You just need to adjust your lifestyle and create a sustainable diet.
I recommend a healthy breakfast (something like oats with some fruit)
Then a healthy lunch, maybe some form of wrap or salad combined with a source of protein.
Then a good dinner, carbs mixed with protein, ideally home cooked.
You should not drink any fizzy drinks, try drink water instead, avoid snacking but eating fruit is ok. And of course, try implement exercise such as walking and any other activity.