Pocket 'rockets' 300ml (and other) small sake bottles
One of the best things about 300ml 'pocket rockets' is that you can try a wide variety for a reasonable price. They're also good in that you can try a sake and if you like it you can get it's big brother 720ml or 1800ml version. They are a nice size to enjoy with your meal. And of course, they're easy to carry around. They even fit in your pocket.