Emperor or no emperor, you still need to eat your spinach when your mother tells you to. We all know about the lavish dinners these guys enjoyed, with mice dipped in honey, flamingo tongues and stuffed udders, but they still had to get their daily intake of vitamins, right?
And some emperors liked their veggies more than others.

His military victories were based on cucumbers. Tiberius loved cucumbers so much, he couldn't go through a day without them. So, during his military campaigns, his slaves brought along mobile greenhouses, in with cucumbers were planted in layers of prepared soil put in carts, and then covered to protect them against the harsh weather of the North.
Who knows, maybe he would've never made it as Augustus' successor without cucumbers.

Well, he was a weird one – because he retired, something unthinkable for an Emperor. He took his complimentary gold watch and moved to Dalmatia, where he enjoyed the sun and the sea in his last years, and took up farming as a hobby.
He lived long enough to see his carefully implemented ruling system fall apart, and the Empire torn by civil wars once again. People came to his palace to beg him to return to work – you know, to be emperor'n stuff, to which he replied: "If you could show the cabbage that I planted with my own hands to your emperor, he definitely wouldn't dare suggest that I replace the peace and happiness of this place with the storms of never-satisfied greed."
Some reports suggest that Diocletian committed suicide three years later. Maybe due to a bad crop season.

Others say that both Caesar and his infamous mistress Cleopatra enjoyed pickles. You'd hope they invited their guests to the luxurious palaces in Alexandra to something more than a pickle party.