Only fruits and vegetables for diet is going to make you weak, bring down your metabolism and you will lose muscle mass as well. Your body requires all the macros(carbohydrates,fats,protein) and micronutrients (minerals, vitamins) and water in proper proportion. Fruits and vegetables will only provide fibers,vitamins and some minerals but what about fats for hormone synthesis and protein for muscle growth? Avoiding macros will suppress your immunity and make you fall sick often.
Don't ever crash diet. Instead, follow a proper diet and exercise routine.