For rehydration I prefer Ringer's Lactate solution. It replaces most of the essential electrolytes and reduces acidosis, which can accompany such ilnesses. It's usually given intravenously, but can be ingested easily enough, and doesn't taste bad.
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)