You could absolutely use the your assigned Gainful Hydration formula prior to exercise, in the same fashion that you would use Gainful’s Pre-Workout blend. Both products will benefit your exercise and recovery, but in different ways.
The Hydration formula is intended to properly hydrate you so that you can perform at your best by delivering an specific and ideal amount of electrolytes to your cells based on your workout frequency, intensity, and sweat levels. A key difference is that the Hydration formula can be taken at any time of day to hydrate you more efficiently than water alone. You want to make sure that you are hydrated throughout the entire day, and not just right before/during exercise.
What makes the Pre-Workout different is that, it is intended to be used right before exercise to give you a "boost" by including beta alanine, which has been suggested in research to improve exercise performance and endurance. The beta alanine is what gives you that tingly sensation when the Pre-Workout kicks in. It also contains and L-citrulline, which is another amino acid that is believed to cause vasodilation, or widening of veins/arteries, which improves overall blood flood to and from the muscles. The Hydration formula does not contain either of these amino acids, or any of the other amino acids found in the Pre-workout which are present to aid with post-workout muscle recovery. Gainful’s Pre-workout supplement contains 150 mg Caffeine, and you can decide whether or not you want caffeine present in your Hydration formula.
As you can see, they both are useful for making you feel your best while exercising. The Pre-Workout is more ideal if you are looking for something to power your workouts more directly and acutely, while the Hydration is more of a foundational supplement that keeps you hydrated and feeling good throughout the whole day. You can substitute the Hydration formula in for the Pre-Workout if you'd like, but you probably won't feel that same burst of energy that many get from the amino acids found in the Pre-Workout blend. It will simply help you by being a hydrating supplement.
Be aware that if your specific Hydration formula contains caffeine, the pre-workout + Hydration formula will contribute 300mg of caffeine, which is a significant amount. Always be sure to assess your own caffeine tolerance. For reference, a regular strength cup of (8oz) coffee contains about 100mg of caffeine.