I’ll Pump You Carries a huge selection of Non-Stim Pre-Workout Supplements. What are they? Non-stim prework supplements are similar to pre-workout supplements, but it does not contain caffeine or stimulants. Some may find that stimulants increase jitteriness and negatively impact their hormones and sleep. A non-stim pre-workout is a perfect option for those wanting to avoid caffeine or the crashes that may come with stimulants.