I have two little eggplant plants that didn't die in the heat wave, but I have never grown them before do they need to be treated like Tomatoes? (2nd year with those)
Mine didn't need one last year, but I caged it anyways. I did the Japanese Eggplant which are small and slender, I would think a larger eggplant would be a bit weightier and could probably benefit from a cage.
Or at least a stake... if you want to go the cheap easy route, I would start by staking it instead.