What is a dollar made out of?

If the dollar is a bill it is made of paper. It is 72% cotton and and red and blue (primarily) polyester fibers. The exact formula of the paper is a closely guarded secret to prevent counterfeiting.

Coins that were minted in 1935 or earlier are 90% silver, 10% copper.

those minted in 1971-80 or 1999, Eisenhower / Anthony design are 75% copper / 25% nickel over a pure copper core.

Those minted in 2000 or later, Sacagawea or presidential portrait design: Copper-nickel-manganese alloy over a pure copper core.
The USA dollar is made of cotton.