Most of the text on the yakult bottle is its claims about being good for you, healthy food, etc. Not going to bother with all that since it all just more or less says the same thing.

why yakult is always related with suigintou? i don't get it..

It's explained in her wiki.

I love this drink so much.
But I really hate how the only way to get it is through very small bottles that cost about $5 or so a pack(comes in like 6) and you can drink the entire thing in 4 seconds.

Yeah.....I wish they replace milk with these. It would make the world a better place and people would actually want to drink it(unless they don't like it)