take l carnitine with bcaa Amino Acids Powder - L-CARNITINE 500MG - Supports Fat Absorbtion Carnitine to help your body use stored fat as fuel during training Pre-Workout+BCAA+L-Carnitine – iGenetics Nutrition
Description
*NRV: Nutrient Reference Value for an adult

In addition, betaine can also be synthesized de novo from dietary choline in the mammalian liver and kidney via a two-step enzymatic process in which choline is first oxidized to betaine aldehyde by choline dehydrogenase

The GLP-1 fatigue guide discusses this issue comprehensively
It is naturally present in food, although dietary intake may vary and is commonly taken as a standalone supplement