Caffeine seems to cause spikes for some people and not others. Not sure if there is any logic to determine if you are a caffeine high or not.
As for foam soap, I am sure it is not the only hand cleanser which can affect BG as sugar is often added to soaps to increase the size and stability of the bubbles. I know alcohol wipes can affect BG which is why paramedics clean fingers with water prior to pricking.
Another thing to be aware of, although it is definitely in decline, is newspaper ink can raise BG if you have it on your fingers.
If my hands are not clean and I need to finger prick, I follow the paramedic approach to avoid contamination and just use water.
I also avoid finger pricking in toilets. The tables of a cafe are cleaned more often and, if anyone notices and is offended by a very short medical procedure that can keep me alive, they can look away.