Can dehydration cause white fuzzy tongue?

Yes and no: The lack of eating that goes along with an illness/dehydration allows the older tongue cells to heap up and get fuzzu.Normal tongue health requires the mechanical action of eating to strip the fuz that would otherwise build up.

Maybe : Dehydration may decrease your salivary flow, which is a natural protector of oral tissue.

Yes but other issues: Yes, but there are many other causes of "white fuzzy" tongue. If rehydration returns your tongue to normal color, you solved your own problem. If not, see a dentist to have it evaluated. There are both benign conditions as well as issues that require treatment.