if life gives you lemons make lemonade is this quote a idiom?

It is not necessarily an idiom, BUT it is a proverb. It means that in a bad situation, something good can occur. This is because lemons are sour, but lemonade is a sweet drink.

I think it's an advertisement for sugar.

It's a cliché.

Whatever.. Mary Poppins would chirrup

'a little bit of sugar makes the medicine

go down' however discordant the yank's

attempt to mimic a cockney accent...; )

Sounds like a would be aphorism

No. It's not a idiom. It's not even AN idiom.

No, it's a homily, or life lesson.

Idiom = a group of words established by usage as having a meaning not deducible from those of the individual words (e.g., rain cats and dogs, see the light ).