I'm sure some will tell you that you shouldn't smoke at all, but that is not your question.
In the baking isle of the grocery store, there is a product called, "Sure Gel". It is not found in the "Jello" isle. You mix the whole package with a quart of water and drink it. The gel coats your stomach and supposedly prevents the toxins from the marijuana from being detected the next day.
I bought two boxes and doused myself with it and I took a test and it was negative, but I cannot assure it will work for you because I don't know when you last smoked or for how long. If this is a urine test, drink lots of water before the test and start to pee before you give your sample. In the middle of peeing, then give your sample as the beginning and the end of doing this, the middle part seems to be the best specimen.
Hope this helps.