If you don't stay in a hotel, can you go to the hotel for a buffet breakfast?

Yes, you can buy buffet coupons directly at the front desk of the hotel. Restaurant waiters only accept breakfast coupons, not cash, so they should buy them at the front desk before eating and give them to the restaurant waiter when eating.

Breakfast is a meal enjoyed in the morning, generally the first meal after waking up in a broad sense.