I used the Nunn tablets on my rides in the Berkshires this weekend. I had no issues with fizzing. I took the cold bottles out of the fridge, popped the tabs in and off we went. I waited the 2 minutes before taking a drink, but other than that, no explosions. I love the fizzy taste. It's like club soda with a splash of juice. They worked well in fairly hot weather, challenging climbs, rides of 53 and 30 miles. I used Shot Blocks to supplement.