If you are in the US, that detergent in the pink box that is made
specially for baby clothes still works best , because who wets
their clothes more than babies ?

Pre-rinse the clothing in the washing machine. Then, wash in hot
water and soap. For “real” diapers, mix soap in a bucket with
water, and, after rinsing the diaper in the toilet, place it in the
bucket until you have a full load.