They are sugar cane. The liquid inside is like a sweet, grey water. This machine squeezes the juice out, into glasses. People like to drink it. If the water evaporates, there is sugar left behind.
Kids like to chew on sugar cane sticks. They suck out the juice, and spit out the stalk. It's kind of like having a huge, sweet toothpick to chew on.
Sugar cane juice can be fermented and distilled. This means it turns into a very strong, clear alcohol. Brazilians mix it with fresh lemon, sugar, and water. It's called Cachassa, or pinga.
This machine is portable. That means the vendor can push it back to his house when he is done at night. He can also push it to a better spot on the sidewalk to sell.