"О, как освежает" doesnt sound bad. Maybe there was something disgusting in the commercial video, not in the slogan itself.

"У ваших бегемотиков не болят животики" is not necessarily bad but quite questionable. Бегемот is something giant and disgustingly fat. To call someone бегемот can have a sense that (s)he eats too much. So with some effort the slogan can be treated like: "Hey, give your fat children our medicine and they will be able to eat even more!"