One of those high protein drinks works quite well.
You do want to try this before the test to know just
how well it works. Also get a good nights sleep. Its better to study less the night before the test so you can get the sleep, then pull an all nighter.
All meds have a time of duration. He is taking the Adderall in the afternoon because the V was no longer working. But, you can't add an Adderall at the same time and expect a longer duration.