I could eat on chemotherapy, was not throwing up, etc. but the chemicals disrupted my electrolytes (essential minerals). I even received a potassium IV drip at one point. I noticed that Gatorade, electrolyte powders and Propel helped. I like Propel the best because it doesn't have a lot of added sugars (though the unnatural sweetener in it, might not be good--I reason this because diet drinks are so bad for us) but we only need these special drinks when there are things going on in our life like strenuously exercising, having sweaty fevers, health issues etc.