With a little preplanning its easy enough. If i just spent 1000 usd to plan my end i would not want it to go to waste. (I have already)
Glass medication bottles are easy enough to source to transfer something into and destroy the original packaging. In almost any house or apartment there are places where nobody would want to look. Nobody would unbolt a toilet and look under it.
If you feel the need to absolutely destroy the evidence by all means flush it completely.
Too difficult to live, just as hard to die peacefully.