Fasting is a wonderful to time to have in the Lord. It is wonderful! I've never regreted doing a fast, nor have I failed to see God do glorious and wonderful things both in me and for me as a result of a fast set aside for Him, doing it His way.
It is a great way to learn to walk after the spirit and to put the flesh down, or in other words, to gain control over it. I find when I fast it becomes easier to control my tongue, to be kind, gentle, and to stop other addictive behavior.
It is a time of cleansing, for every part of my being, spirit, soul, and body. I am much more sensitive to sin in my life, or ways that are not pleasing to the Lord. My mind begins to clear itself and my thinking grows sharper. And finally, my body rids itself of toxins, thus enabling clarity of thinking, clear eyes, glowing skin, and a host of other things too numerous to list!
Fasting has its ups and downs. Not every moment do I feel wonderful while fasting. It's tough on the flesh in every respect. Sometimes I have gone through periods where I can hardly get off the couch because of weakness. This is not abnormal. It is all part of the process of the body cleansing itself. At this time, don't worry. You'll feel great later, and you'll be glad you did it.
These things happen mainly on a more lengthy fast, although if done in a way that promotes health to the body, you may feel it the second day. Every fast is different, and every body is different. The most important thing though is - don't take in any junk at this time. Whether it is liquid or solid form, a toxin is a toxin!
To answer your question, no, I wouldn't dream of having coffee on a fast. Herbal teas, such as medicinal teas are highly recommended and will aid in cleansing the body if you choose the right ones for that.
If you experience such severe affects when fasting that prevent you from working I would try a couple of things. One, fast when you're off, on a weekend, or possibly taking time away from work to fast if the situation demanded a more lengthy fast. You know your body and what it is capable of. It is best not to start out with a longer fast, but to do short ones. The other thing is, prepare to fast. This is vitally important to minimize the negative physical discomforts. This done by slowing down on the caffeine prior to the fast. Also, eat only raw fruits and vegetables for two days before you fast Or, for three days have oatmeal for breakfast (and not sugary, instant) with only raw fruits and vegetables the rest of the day. And yes, you can eat a salad without dressing. You don't need those chemicals in most store bought bottled salad dressings. Doing this will greatly reduce hunger, headaches, and more. No fast is easy. Suffering is part of it, but the benefits far outweigh the price you pay.
