"The evil child is drinking coffee."
Translation:Złe dziecko pije kawę.
"złe dziecko" makes as much sense as "evil child" = not much. The adjective "zły" seems very basic, but it's surprisingly hard in use, and I believe it has been introduced too early, which results in rather awkward sentences.
The word for "naughty", "misbehaving" child is "niegrzeczne".
"zlę" is not a word, you meant "złe" here (although perhaps it was just a typo, 'alt' button used in the wrong moment).
"piję" is 1st person singular (I drink/I am drinking). The appropriate, 3rd person singular form (he/she/it drinks/is drinking) is "pije", with a normal 'e'.
And now, the main point: "jest pije". No, it's wrong. When you think of an English construction like "is drinking", don't think of it as if it was two verbs: a form of "to be" and a form of "to drink". There's just one verb, a form of "to drink". You only translate one verb. "jest pije" in Polish makes as much sense as "he is he drinks" in English.