The simple answer is no, there is not something that can be sprayed on plants to give them protection from late spring freezes. However, there are all sorts of trials and testimonials using foliar potassium (Nutri-K, Agro-K), carbohydrates, and sugars sprayed onto plants a few days prior to cold temperatures setting in to help plants survive. Each product is basically acting like antifreeze (prevent nucleation) in the cell to prevent internal freezing and cell bursting. It is very difficult to get good data on farms on in research field trials to verify when/how/if these products actually work. Conditions vary so much from site to site and year to year that we don't have replicated data to stand by (remember that ISU is reserach based guidance). At this time, I cannot say there is solid evidence of any product being affective consistently and in replicated in trials. A lot of factors go into it including timing, product, and rate (and probably a bunch of other things).