For 99% of Polish verbs, there is no difference between Present Simple and Present Continuous. So generally those sentences are the same.
That 1% (well, a lot less actually) covers Verbs of Motion and so-called habitual verbs.
There is a habitual verb for "to drink", it's "pijać". "Mały kot pija mleko" = The small cat drinks milk" (and NOT "is drinking"). But the 'normal' verb is perfectly fine for Present Simple as well. Habitual verbs aren't even in the scope of this course, they are not that important compared to other things that are taught. It's good to know about them, but you don't need to use them. There aren't that many verbs that have a habitual equivalent anyway.