Benadryl is prescribed to children as a sleep aid, and dogs and cats to help prevent travel sickness and keep them calm.
Last time I took Benedryl though, (which was just last week) I slept for almost 2 days solid and could hardly move for several days afterwards. Benedryl has an especially high residual effect, at least on me, so I try to avoid it at all costs, but it works, and is very effective.
for nausea specifically though, Dramamine (for car sickness) can be even more effective, but it also can make you extremely drowsy.