Trim the ends of the Brussels sprouts and remove any brown outer leaves. Cut them in half; quarter large ones for even cooking.
Optional: Soak sprouts in warm water for 10 minutes for a more tender center, then drain and pat dry.
Preheat the air fryer to 375°F (190°C) for 3 minutes.
Toss Brussels sprouts with olive oil, salt, and pepper in a bowl.
Place in the air fryer basket in a single layer.
Cook for 5 minutes, shake the basket, then cook another 5 minutes.
Add garlic, shake again, and cook 2–4 more minutes until crispy.
Transfer to a bowl, add toppings if desired, and serve hot.