What?
"Lean" is a mixture of codeine syrup(usually the one with promethazine), sprite(or Mountain Dew, and jolly rancher candies(or any other flavour additive) but the syrup, sprite and ranchers are what makes "lean".
What you're talking about I believe is a CWE(Cold Water Extraction) I have never done that as I have access to codeine linctus, 100ml bottles with 300mg Codeine phosphate in it for dirt cheap.
If you don't have that access then look into CWE and extract the codeine from the APAP which I then think becomes a clear solution? Correct me if I'm wrong I've never done a CWE.
But yeah idk I think you need to research. But I guess you could flavour the extracted codeine solution idk.