Cool Potions

Super Fast Speed Potion For Java 1.17.2 snapshot20w15a:

First get any speed potion in your hand

Then do /reload 1slot @p mainhand:weapon nbt%itemdata (1[30{255(0)amp}sec]value)[0]placehandeler[1][3][{line}remove2](0),+nbt%data{ (1[30{255(0)amp}sec]value)[0]placehandeler[1][3][{line}remove2](0)} <#1>,+ type=nbt%itemdata [code:remove;, <#1>],+ tag=add ="name" [code:remove;,} <#2>1]]]})]}]]])]}))]}]]])]}}}-2]]]})]}]]])]}))]}]]])]}}}end=true

Then do /reload after

Also make sure to replace "name" with the name you want to call the potion

If that doesn't work or you're on a different version then do it manually by doing /console inspect. Then /edit. Then /effect give @p minecraft:speed "seconds" 255

Also make sure to replace "seconds" with how many seconds you want the effect to last