Ingesting gasoline is deadly in far smaller doses due to something called hydrocarbon pneumonia. My dad very nearly died as a result of having a tiny amount get past his throat while siphoning gas to a small engine's tank.
If you must siphon gas, go buy a cheap "pump siphon" from Canadian Tire.
This only compares the risk of death, not other health problems. Also, gasoline is way more readily available in pure form than most other substances, and nobody would drink it voluntarily.