Setup: Place a hopper above a brewing stand.
Steps: 1.Fly above the hopper and throw the splash potions down into it (using right mouse button default) (I tried healing and regeneration and both were bugged).
2. Toss the item into the hopper (using Q key default).
3. check brewing stand and there will be 2 potions of the type you threw.
Additional Example: if you throw (right mouse button default) several splash potions of harming at the top of the hopper and then toss the splash regeneration potion (Q button default) you will have 2 splash regenerations in the stand.