They’re free, fit in the tiniest pockets, are found around the globe…and kids can’t keep their hands off them. In sachet, cube, or tube form, sugar packets make perfect vacation mementos. But not all are created, um, equal—the ones worth keeping are those with local flavor. Some are unique to a restaurant or city; others pay homage to the animal kingdom or to sugar itself. Clubs and "sucrologist" conventions have been crystallizing across Europe, and you can find collectors’ Web sites in languages from Italian to Czech (the.millerfamily.name/sugar is a good English example). So let your children stash their favorites—baseball-card holders work well for storage—and you’ll have an especially sweet reminder of your trip.