Green’s Dictionary of Slang

1. (Aus.) alcohol, liquor.

1914		Sport (Adelaide) 27 Mar. 3/5: Dobbie M, the cigar king, had too too much lemonade on Saturday, night. Was it because he got a blue duck from a strange tabbie ?
2021		J. Ellroy Widespread Panic 87: I ordered a putcher of [...] high-test lemonade. 150-proof bourbon.

2. (US) urine.

1977		S. King Rage in Bachman Books (1995) 14: I needed to whiz piss make lemonade whatever you wanted to call it.
1983		S. King Christine 34: You act like you’re going to make lemonade in your pants.

3. see lemon n. (1e)