all right, so, you are FAR, FAR away from a pure product.
I am a self proclaimed master of extracting codeine from just about any preparation.
The best thing to use is ASA & C formulation (available in canada only)
Aspirin has a very low solubility in Ice Cold Water, and so does caffeine. You should grind up the pills (like, 40 or so), and pack them insinde a 60CC syringe, with a little bit of coffee filter in the bottom to prevent the powder from coming out. Then you gently pack this powder (tap syringe on stone counter top) and add water and the plunger. You collect about 5cc's at the bottom, and discard the rest.
Now if you evaporate the water you will end up with Codeine Phosphate and some residual Aspirin and some caffeine. But it beats large volume CWE's for sure. At least in my humble experience of doing uhm... some 3000 extractions in my lifetime.. it works better than disolving everything in 100ml of water.