SIS GO Isotonic Energy Gel – 6 Pack. When you commit so much time, energy and determination to being the best you can, you want a sports nutrition partner that truly understands physical endurance – one that you can trust to provide the best and most effective solutions. Used extensively by elite athletes who only accept the best, SiS Go Isotonic Gels are a breakthrough in energy delivery. They are the world’s first isotonic gels to deliver carbohydrate energy without the need for extra water and have been tested in high intensity exercise studies. Enhance your performance by using SiS Go Isotonic Gels during endurance sessions to help you avoid flagging.