If you're going just one more day without water touching your scalp, this popular Living Proof Perfect hair Day (PhD) Dry Shampoo ($14-$36) is a quick refresher. Not only are there sweat- and oil-absorbing powders alongside odour neutralisers, this dry shampoo has the brand's patented healthy hair molecule that lets these substances (and whatever dirt they've absorbed) easily rinse out afterwards, too.