If I translate it into Japanese, I'd say 「（あなたって/あなたは）優しいですね」 We tend to translate "sweet" as "kind" or "nice." If you say it to your daughter or perhaps to your pet, you could translate it as 「かわいい」. So, it varies depending on what or whom you refer to.

Okay so, I'm not a very reliable source, since I'm still a beginner in Japanese, but to the best of my knowledge it's "Anata wa amai desu."