Why buy the water? Traditional shampoo bars are great for the environment - no plastic bottles or no heavy shipping weights. Just rub the bar in a circular motion directly onto you hair and work up a healthy lather. Rinse thoroughly.
Try Sallyeander’s suggestion for a natural conditioning rinse - a mix of cider vinegar and clean water. This hair care regime was the norm a century ago. Shampoo bars are ideal for camping.
Apple and Ginger - for oily hair
Calendula and Chamomile - for babies, blondes, or colored/permed hair