These drinks are calorie free, which technically should help people lose weight and prevent sugar-related diseases like metabolic syndrome and diabetes. However, the evidence for these beverages having any use is completely nonexistent.
The classic approach to performing supersets is to work two opposing muscle groups back to back without any rest between sets. This technique is usually applied to antagonistic muscle groups such as biceps and triceps, chest and back, quads and hamstrings. An example of a superset would be one set of biceps curls immediately followed by a set of triceps pushdowns.
If you think you are going to fail, stop 1-2 reps before that failure feeling. You can still do several sets and get a pretty high volume of reps, but just no FAILURE reps. I like a Super Set Circuit for this type of workout. For instance do several sets 10-15 sets of 5-10 pullups / dips and 10-20 pushups per set..