Taking pre-workout supplements every day is generally considered safe, but it is not recommended to do so on a daily basis. For optimal results and to reduce the risk of developing a caffeine tolerance, it is best to take pre-workout supplements 3 to 4 days a week. Most pre-workout supplements contain all-natural ingredients that are generally safe for most people, so taking them every day is not an issue in theory. However, there is one drawback that may prevent you from doing so - your body will get used to it and develop a tolerance to its ingredients, meaning you'll need to take more of the supplement after about a month or two.
It is not recommended to take pre-workout supplements if you have underlying health problems, are becoming dependent, have nervousness or insomnia, or if the pre-workout contains substandard ingredients. The amount of BCAA in pre-workouts can range from 1 to 3 g per serving, while BCAA supplements alone offer between 5 and 7 g per scoop. Other compounds found in pre-workouts can cause side effects such as diarrhea if not mixed properly with enough water according to the manufacturer's instructions. If you decide to take pre-workout supplements every day, I recommend consulting organic supplements before training.
Alternately, you can buy a caffeinated pre-workout and a caffeine-free one and alternate them throughout the week depending on your needs for that particular day. It is also important to avoid pre-workouts that contain artificial additives and high amounts of sugar.