The locals (and I mean the ones who were born and raised in Belize) told us that as long as you do not carry a bottle, it is okay. They informed us that as long as the beverage is in a cup, all is good with authorities. The only problem that you should keep in mind is that it is virtually impossible to drive with a drink in your hand anyway as the bumps cause you to spill more than you can actually consume. For a short drive, it's not worth it to drink and drive.