Foods high in rapidly absorbed carbohydrate cause the quickest spikes. The biggest culprits are usually sugar-sweetened drinks and fruit juices, sweets and desserts, and refined starches such as white bread, white rice, and many breakfast cereals. Portion size matters as much as the food itself.
Fibre, protein, and fat slow digestion, so eating whole grains, legumes, vegetables, and combining carbs with protein generally produces a gentler rise. Individual responses vary, which is why some people use monitoring to learn their personal patterns.
This is general nutrition guidance, not a prescription. Diabetes eating plans should be personalised, ideally with a dietitian, and balanced against your medications to avoid lows. If you take insulin or certain tablets, carbohydrate amount directly affects your dosing, so coordinate any major diet change with your care team.