Cut the chicken breast into roughly 3–4 cm cubes. Cut the peppers into similar-sized chunks. Cut the onions in half to create thick slices.
Thread the skewers in this order: red pepper, onion, chicken, yellow pepper, onion, chicken, green pepper, onion, chicken. This makes about 12–15 skewers depending on piece size.
Season the skewers all over with chicken seasoning, salt and pepper.
Heat 3 tablespoons rapeseed oil in a large pan over medium-high heat. Fry the skewers for 10–12 minutes, turning occasionally, until the chicken is golden brown and reaches 74°C (165°F) internally.
Remove the skewers from the pan. Add the water to the pan, scraping up the browned bits. Stir in both ketchups and the sugar, then season with salt and pepper to taste.
Return the skewers to the pan and simmer for 10 minutes.