sky – tee-en
Written as tiān or tian
To remember that sky is pronounced tee-en (tian) in Mandarin Chinese, use the following mnemonic:
In the sky was a flying tea pot with an engine (tee-en).

Tones
En (engine) is a 1st tone with — as an accent.
Associate engine, a 1st tone, with a string or tie or tying or knot. See Tones and Mnemonics.

You have to pull the string to start the engine.
Remember
En = 1st tone = —