The best way to start a shift, apparently, is with a “morning bar” like the ones Thom can get from the vending machines aboard Angel Fish. Putatively a meal-replacement, the main food groups on offer seem to be bulking agents and stabilisers: it’s a block of mainly starches, gums, low-density granular pseudodextrins, and other things designed to eke out a bland cocktail of water, xylitol, protein, and caffeine. That’s assuming those ingredients are available cheap enough–there’s nothing stopping the manufacturers using inedible bulking agents, like petrochemical sawdust or plastic swarf bought in bulk.
Anyway, it’s clearly not the most enjoyable thing in the galaxy. But it’s shelf-stable, making it cheap. It will survive being in a pocket all day without melting or being mashed up. It seems to be available almost everywhere, albeit with superficially different branding as sold by various subcontractors. And it’s so disgusting, dry, rock-hard and hopelessly undernourishing that it often takes Thom several attempts to bring himself to bite into it–meaning that that small investment can last for hours.