Caffeine takes about 20 minutes to metabolize to the point where it can suppress adenosine reuptake. This is how people do “coffee naps”.
Twenty minutes is plenty of time to write down 10 original ideas. Why not chug your coffee (or use caffeine pills), then spend the following 20 minutes writing your ideas? Alternately, sip your coffee while writing your ideas — and take advantage of the much slower ramp-up in the effects.