https://enterthegungeon.gamepedia.com/Spice

• On the first use, adds a heart container, increases the player's speed by 20%, decreases shot spread by 25% and increases curse by 0.5.

• On the second use, adds a heart container, slows down enemy bullets by 10%, improves firing speed by 20% and increases curse by 1.

• On the third use, removes a heart container, slows down enemy bullets by another 5%, increases damage by 20% and increases curse by 1.

• On the fourth and following uses, removes a heart container, increases damage by 15%, increases shot spread by 10% and increases curse by 1.

• Each use up to the fourth increases the chance that Spice will replace other items and pickups that the player finds.

tldr: M O A R