"What do you drink?"
Translation:तुम क्या पीते हो?
Use आप for strangers (like shopkeepers) and everyone you meet for the first time. As you get to know them better, you can progress to तुम if they are around the same age as you or younger. You can also take cues from what form they use for you.
(With someone much younger than you in casual settings or with children, you can start off with तुम itself).
With transliteral keyboard - 'kya' क्या; or directly you need to long-press क to be able to select a sort of first half of it (I can't type it alone) then य for क्य and finally select the full word क्या at the top (alongside other options for different vowel endings). [I'm using Google's 'G-board' on Android, I imagine others are similar.]