I always feel hungover after a hypo/manic episode too, but I guess it's because our bodies are trying to catch up on some much needed sleep. So then we're all groggy and "out of it" because we're overtired. Doesn't help that depression alone makes you get more sleep, and the time change DEFINITELY doesn't help either.

Do you think you could go to bed earlier? Sounds like you need more than 7 hours a night if you're drinking that much coffee.