These five BPA-free handheld soft flasks perform well in tests from hydration experts. The Nathan Soft Flask holds 20 oz, has a bite top, is soft and collapsible, and is dishwasher safe. The Pinnacle 14 oz uses ExoSpine, weighs about 2.5 oz, and adds expandable pockets. The 500 ml Running Water Bottle includes two zip pockets and a towel pocket. HydraPak’s 150/250 ml collapses to save space, and the 18 oz Pinnacle adds insulation. More details come next.