"Can I get some water?"
Here. I hope this helps.
★これ - "this", something you're holding.
★それ - "that", something you're not holding but something somewhat near to you.
★あれ - "that over there", farther than それ, far from you and whom you're speaking with.
★ を - object particle; indicates object of verb/action.
★ ください - (polite) requesting to give/to do something.
English: "Please give me water" or "Can I get some water?" as per example given.
"Please give me this"
【speak/talk】【<-- please do】
"Please talk [to me]" or "Let's talk", etc.
【stop】【<-- please do】
I would make a correction here, because これ/それ/あれ are not dependent on their distance from just you, but also from the person you are talking to. これ is not necessarily something you are holding, but something that is closer to you than to the person you are speaking to. それ would be better defined as something that is closer to the speaker than to yourself, no matter how far the speaker is from you.
A literal translation would be "water please".
水 being water, を to link the request to the subject, and ください being please.
If you consider it as such, no question mark is required as it is a request not a question.
In duolingo, it appears to be phrased as a question to make the request more polite only - though it is not the most literal iteration it helps relay the effect of adding お.
水 (4 strokes) Water, flood, fluid, Wednesday
••Reading•• ▪Kun: みず(Mizu)、みず- (Mizu-) ▪On: スイ(Sui)
•••Words Starting with 水••• ▪ 水曜日《すいようび/Suiyoubi》: Wednesday ▪水道《すいどう/Suidou》: Water service ▪水泳《すいえい/Suiei》:Swimming ▪ 水平線 《すいへいせん/ suiheisen》:Horizon ▪ 水割り《みずわり/Mizuwari》: Alcohol
•••Words Ending with 水••• ▪ 香水《こうすい/ Kousui》:Perfume ▪ 淡水《 たんすい/Tansui》:Fresh Water ▪ 噴水《ふんすい/Funsui》:Fountain ▪ 洪水《こうずい/Kouzui》:Flood ▪ 海水《かいすい/Kaisui》:Ocean Water ▪雨水《あまみず/Amamizu》:Rain Water