Personally, I've tried some preworkout supplements that were loaded with caffeine and I hated them. I don't drink soda or coffee, so I am not used to caffeine. I felt jittery, my skin crawled, and my mind was racing to the point that I couldn't focus on my lifting. I felt a little stronger and was able to lift more, but it felt very chaotic. If you have a higher tolerance for caffeine, you may get different results. But I don't want to try any more caffeine ever again.