Ramune is too dangerous for beginners! Doesn't really matter but Mayu's "Can't drink ramune well" is good song but it's not very well known and that's sad. Mostly to me though(゜□、゜)
R.Smith, the next 4-koma in the series have comments which explain the joke. Basically, ramune bottles have a marble in the neck. To drink, you have to push the marble backward.
Ramune tastes like... well, like coloured water. Eww.
Not sure what flavor you had, but I used to have the stuff "imported" from about 80mi away by people who visit the city because it was so much better than regular soda. But, obviously, much more expensive. The murder potential of those thick bottles is immense.