Beetroot is a common addition to many pre-workout blends as it has been shown to increase nitric oxide production which can enhance blood flow and pumps. This can also benefit endurance performance, but likely won’t have any immediate effect on strength or size gains. There are several ways to take beetroot to get the optimal dosage of nitrate, so pick your favorite and head to the gym!
Reference: Hoon, M. W., Johnson, N. A., Chapman, P. G., & Burke, L. M. (2013). The effect of nitrate supplementation on exercise performance in healthy individuals: a systematic review and meta-analysis. International journal of Sport Nutrition and Exercise Metabolism, 23(5), 522-532.