Breakfast was bacon pieces and cinnamon bun paired with a drink of Tang. There was also pea soup and tuna salad, standard Apollo-era space meals.
These were mainly dehydrated and semi-moist foods, some of which required heating and some in their natural state (mostly nuts). There was no problem with them nutritionally, but tasted barely passable.
The space food of later generations was greatly improved, having benefited from the advancement of food preservation technology. In Zhang Heng's era, NASA would provide astronauts with an option of more than 180 types of food and beverages. You could even have chocolate ice cream on the International Space Station (of course, a very extravagant thing even for now), which helped a lot in keeping the astronauts' morale high throughout their months-long stay and lonely tours above our planet.
For now, however, Zhang Heng and the other two candidates wouldn't get to enjoy this privilege.
