Don’t Have to Make a Mint on This One: Metro Electro Offers Challenge to Smartwater    Soma Beverage, which has surprised lotsa folks with how far it’s been able to take mint-water concept, is ready to make 1st foray beyond self-invented segment with electrolyte-infused Metro Electro Micronutrient Water.  New SKU from SF-based co offers alternative to brisk-selling Glaceau Smartwater with healthy larding of electrolytes, antioxidants and zinc but no flavor, no sweeteners and no mint, said co-founder Matt Collins.  “Like a Vitaminwater, minus the sugar and flavor,” and healthy improvement on both Vitaminwater and Smartwater, he told BBI.  Line joins other Smartwater wannabes hitting market, including O Water Sport.  Given broader hydration role, Metro Electro will upsize package from distinctive slim 500-ml plastic bottles of core line to 20 oz, but will retain enough graphic copy cues from mint line to make it clear it’s part of family.  Larger-size packs also are under consideration.  “It’s definitely a Soma Beverage product, but we didn’t want people to think it’s a mint product,” Matt said of slight distancing effort in branding.  Brand is in final quality-assurance phase and will be pitched to chains starting in mid-June.