Nothing is good or bad, only thought makes it so. Coffee is not bad either, nothing is bad. Coffee just has a certain range of properties / effects that are not compatible with a lifestyle of predominantly fruits and vegetables. On a vegan / omnivorous diet rich in fats / oils and amino acids (protein) coffee can make you feel good, after all it is a mood enhancing central nervous system stimulant that increases the movement of serotonin and dopamine in the brain.
Coffee increases blood circulation to the brain, especially the cortex and frontal cortex thus enhancing your sense of identity and ability to process more information in a shorter period of time; it increases heart rate, warms the chest, liver and head and can be used therapeutically, but only temporarily, to treat depression, low mood, drive, spirit or willpower; it is known as a cholagogue which purges your liver and gall bladder of excess fat including alcohol and bile acids. It is important to note that the former benefits are obtained at the expense of the blood, kidneys, liver, adrenals and skin by way of irritating the kidneys and adrenals over time as it dehydrates the system and stimulates the excess release of noradrenaline. Because coffee is a stimulant it effectively steals from tomorrow for today. Meaning that it causes the body to consume more blood, fluids, minerals and vitamins etc so that the ‘high’ can be achieved.
Therefore, on a low fat, low caloric lifestyle of mostly fruits and vegetables coffee will send you into a state of depleted overdrive. It is thus not recommended to consume coffee during this challenge, unless in the form of a coffee enema which should only be done not more than once or twice at the beginning of the challenge.
Many alternatives are available in Superfood and Herb form that rebuild and strengthen the kidneys and adrenals, liver blood and heart over time.