If you want to start a fire, it's best to keep some matches or a lighter on you, but there's always the possibility you won't have one. Secret Tips from the Yumiverse created a guide to start a fire with something you probably always have access to: water.
If you were the kid to sit around burning ants with a magnifying glass, the idea will be familiar to you. You use the water inside a jar to focus the sun's rays on kindling (or Doritos) until you get glowing embers. Once you have the small spark, give a few gentle blows and you have a fire. Obviously this only works during daylight, but it's still a good trick to know. Check out the full guide over at Secret Tips from the Yumiverse.
How to Start a Fire with Water [Secret Tips from the Yumiverse]