This datapack will implement the Haste Potion into Minecraft.
Basically what this datapack does is makes a potion that gives you the haste effect.

In order to use this datapack first download it, extract the zip file and put it into the datapack folder of your world. Then install the supplied resource pack for the haste potion texture. Once you do that you should either restart your world or use the "/reload" command. Now, to use it first craft it according to the crafting recipe in the images section. Then just drink it like a normal potion and you should get the haste II effect!