Boost your body and mind These capsules with a high dose of caffeine are a great idea for your workouts or anytime when you need some energy boost. The dosage is simple thanks to the form of capsules and you can easily take them anywhere with you. The most popular stimulant - caffeine has been an essential part of pre-workout supplements for many years. It naturally occurs in tea leaves, guarana, kola nuts, or in the one-and-only coffee.