L Carnitine: Does it help with weight loss? Most energy drinks are loaded with caffeine and sugar, which can cause jitters, dehydration, headaches, and even affect your heart if consumed often. While an occasional drink may not cause harm, regular L Carnitine and Sleep: Does It Affect Rest or Sleep Quality? PDF) A Pilot Clinical Trial on L Carnitine Supplementation in Combination with Motivation Training: Effects on Weight Management in Healthy Volunteers