One analyst with Exane BNP Paribas sees over 50% upside in the better-for-you energy drink brand.Shares of functional energy drink maker Celsius (CELH -0.44%) are down 41% in the last month after Nielsen reported that the company's share of the energy drink market dropped from 10.8% to 10.5% in May.This market share dip, paired with worries about Celsius struggling to lap the triple-digit sales growth rates it saw following its partnership with PepsiCo, caused Wall Street to take a cautious stance toward th ...