Health and Human Services Secretary Robert F. Kennedy Jr. is challenging two major coffee chains — Dunkin' and Starbucks — as part of his "Make America Healthy Again" initiative.Kennedy recently called on the two companies to prove their high-sugar drinks are safe for teenagers and suggested the Trump administration could place limits on your morning cup of coffee."We're gonna ask Dunkin Donuts and Starbucks, show us the safety data that show that it's OK for a teenage girl to drink an iced coffee with 115 grams of sugar in it. I don't think they're gonna be able to do it," Kennedy said late last month.Massachusetts Gov.…