In a large bowl, stir oats, flax, protein powder, and salt. Break up any protein clumps—nobody wants a powder bomb.
Stir in peanut butter, honey, and vanilla. Use a sturdy spoon or clean hands. It'll look crumbly, then come together.
Add 1–3 tablespoons of water or milk, 1 tablespoon at a time, until the mixture presses and holds without cracking.
Mix in chocolate chips. If they try to escape, you're doing it right.
Scoop about 1 heaping tablespoon per ball (roughly 1 oz/28 g) and roll into 16–18 balls.
Refrigerate 20–30 minutes to firm. Not required—but it helps them hold shape for the gear bag.
Serve 1–2 balls 45–90 minutes before activity. For longer tournaments, 1 ball between games keeps the tank topped off.