Soda may explode in checked luggage because of the pressure in the hold. If you absolutely need to bring back a soda from your trip, pack it in a ziptop plastic bag that is closed completely. That way, if it does explode, the sticky soda gets all over the bag and not all over your clothing. We've brought beer back on two separate flights, one domestic and one international. When we flew with a six-pack internationally, one of the six beers exploded but the other five did not. When we flew with beer domestically, it did not explode. Of course, those are anecdotal not scientific studies, but they're worth noting.