[Aquila]

Is injestion of caffein and nicotine sin?

I don't think it's a "sin". However, I see it as unhealthy; just like eating a quarter-pounder value meal from McDonald's for lunch every day is unhealthy.

When asked about smoking being a sin or not I've often said, "Smoking may not keep you out of Heaven, but it just might cause you to end up in Heaven sooner than you planned, and with far more suffering in the process."