I don't know about coke, but I think
fasting should be relaxed significantly.
Considering we're talking about 50ml SN absorbed within 1.5h – we don't need full emptying of entire small intestines. A good goal is to empty stomach and
most of the small intestines. That is usually achieved within 5-6h after a modest meal.
Liquids travel rather quickly. Water in stomach empties into intestines within 5-10m. It undergoes no processing, absorbed to blood within 30-60m (osmosis).
Water could be minimized 2h before – and halted 1h before.
Small amounts of simple sugars are relatively quick. But they do involve some stomach churning/breakdown (~15m). They do change pH (for ~ 1.5h). And they take longer to be absorbed in intestines (~ 1.5h-2h).
Simple sugars could be minimized 4h before – and halted 2h before.
That said coke is not just water+sugar, but it's not far off. Stomach pH returns to balance around 1h
after it empties. As mentioned, intestines empty of sugars within 2h. You can draw your own conclusion.
If
I really really really had to – I would drink a glass 2h before,
at most. That should be rather safe to empty 90% intestines and return stomach pH to balance.
In graph we're interested in hours 3.0-4.0, and pH (green) return to normal:
View attachment 24689