Fruit, nuts, trail mix, diced meats- that's common at my girls gyms. Those are quick and easy, and not too messy. At three hours for practices, I would be surprised if there was a regular snack break though. My kids didn't see regular snack breaks till they hit the four hour mark. My ODDs new gym goes 4.5 hours some days and still no break. The girls do shove a quick bite into their mouths between rotations when they need it. We've also had gyms that had restrictions and recommendations on snacks allowed at the gym, so make sure there is no official guidance on the subject.