During the winter, it's easy to find excuses to stay inside and avoid adult responsibilities. It's cold. There's snow all over, and it's covered with miniature ice canyons made of the neighbor's dog's pee. But sometimes putting off errands can lead to desperate situations, like realizing after turning the shower on that you're out of soap and shampoo and it's too late to run to the store and make it to work in time and in clean form. Don't panic— let's MacGyver out of this.
Depending on the extent of your smelliness and how presentable you need to be after you leave the house, you could just shower sans soap, rinse off, and, if you wear your hair long, comb it back and twist it into a bun or something, which is my standard hairstyle for when I don't want to terrify bystanders as I thunder through the streets with unkempt and dirty Uruk-hai hair and a sour look on my face. But if it's gotten to the point where you can smell yourself, you're going to have to bite the bullet and wash with something that isn't soap, unless you want everyone on the train to know you're The Smelly Kid. Don't be The Smelly Kid.
Going shampoo-free (even for a short period of time) isn't that uncommon; plenty of people avoid commercially produced cleansers because of allergies to the ingredients, or an aversion to the chemicals they contain. Devotees to the practice usually cleanse with a paste that's made of equal parts water (or apple cider vinegar) and baking soda— a couple of tablespoons of each. Mush it together and put it in wet hair. Scrub, then rinse. You can also mix olive oil and eggs to make conditioner— beat eggs with a few drops of olive oil, apply to your hair, wait a few minutes, then wash off. Use cold, not hot water, though; hot water could start to cook the eggs onto your hair and no one likes to hang out with the girl who smells like a bird abortion. Also usable, if you have something to mask the smell: beer or a diluted mix of vinegar and water. Aloe vera gel mixed with some hand soap. Mayonnaise can be used as conditioner in a pinch, as can fabric softener. Just start rubbing shit on your head and pray the water doesn't turn off mid-rinse.
If you're out of shampoo but still rolling in body wash, just use that on your hair. Shampoo and body wash are basically the same thing (five professional hair stylists just fainted. Someone fetch the Paul Mitchell smelling salts), although body wash has not been clinically proven to give anyone an orgasm in the shower like 1998 Herbal Essences can. Using one thing for both hair and body isn't going to kill anyone.
And, it should go without saying that the opposite is true as well; anything that you use as shampoo can also be used as body wash. Just rinse off, apply the requisite pleasant smelling after products you normally apply, and scurry off to your engagement as though you didn't just spend the last 10 minutes rinsing beer out of your hair. You've done it. You've conquered hygiene.