You can bring on snacks. You can usually bring on soda in cans and soda and water in factory sealed bottles - although there have been some isolated reports where this wasn't allowed. Like the airport, expect to go through a metal detector and your bags through x-ray machines each time you board. And you might want to check your cruise documents for the cut-off time to check in. It is usually 90 minutes before departure. If for any reason you are delayed and the cut-off time is approaching, call them. Have a great cruise.