Halfmilk RBA

Discovered by Cosmo & Kuwaga

Information

There's a rather bizarre oddity that can occur with Reverse Bottle Adventure.

When you empty the contents of a bottle under normal circumstances, the game code will start with a check to see if there is a full bottle of milk (item value 26) in the proper inventory slot. Then, if it finds a full bottle, a half-full bottle of milk (item value 31) will be put on both the button pressed and the inventory slot, regardless of the old bottle's contents.

This leads to an interesting side effect. If the memory address we're trying to use RBA to manipulate stores a value of 26, we can change it to a value of 31 (the same as a half-bottle) by emptying the contents of the B bottle, without needing Bottle Adventure to get a full bottle of milk on B.

Setups for Half-Milk RBA

Half-milk RBA is useless for editing the main inventory, since you can only put a full bottle on the normal bottle slots. You can endlessly perform Half-Milk RBA with item amounts, but you can also just as well use normal RBA to get infinite item amounts.

For example, if you have a fish on B, a bottle with a normal poe on C-Right, and exactly 26 bombchus, dropping the B fish will give you 31 bombchus. However, once you drop the fish, you should immediately swap c-right to a different item (an empty bottle, bugs, or fish will work nicely), so you can recapture the fish on the B bottle without setting the ammo count back down to 25.

Item Amounts
item on c-right	item amount updated
Fairy	Deku Stick amount
Fish	Deku Nut amount
Lonlon Milk (full)	Bomb amount
Bottled Letter	Arrow amount
Big Poe	Deku Seed amount
Poe	Bombchu amount
Spooky Mask	Magic Beans amount †
Bomb Bag (Holds 20)	Water Temple Small Key amount

† - Can be done by getting Full Milk on B, drinking it while the Spooky Mask is on C-Right, then using up 5 Magic Bean, but is pretty useless.

Equipment Subscreen

Halfmilk RBAs
c-right	start items	end items
Goron Mask	Have the Goron Tunic, Kokiri Boots, but not the Kokiri Tunic, Zora Tunic, Iron Boots, or Hover Boots.	You will have the Kokiri Tunic, and Zora Tunic, and keep the Goron Tunic, and Kokiri Boots.
Zora Mask	Have the Master Sword, Broken Sword Icon and the Deku shield, but not the Kokiri Sword, Biggoron Sword, Hylian shield, or Mirror shield.	You will have the Kokiri Sword, Biggoron Sword, keep the Master Sword, Broken Sword Icon, Deku shield, and lose Hylian shield, Mirror shield.

Left-Side Equipment Screen

Half-milk RBAs
c-right	start items	end items
Pocket Egg	Impossible to Half-milk RBA	Impossible to Half-milk RBA
Pocket Cucco	Impossible to Half-milk RBA	Impossible to Half-milk RBA
Cojiro	Have "Bomb Bag (Holds 40)" in you Bomb Bag Slot and "Quiver (Holds 40)" in your Quiver Slot.	You will have "Bomb Bag (Holds 40)" in you Bomb Bag Slot and "Goron's Bracelet" (Holds 40) in your Quiver Slot.

Quest Status Screen

Half-milk RBAs
c-right	start items	end items
Odd Mushroom	Obtain an Odd Mushroom RBA value of 26 and empty your B bottle	You will now have a value of 31
Odd Potion	Have Zora's Sapphire, Goron's Ruby, and Song of Storms, but not Gold Skulltula Count, Gerudo's Card, Stone of Agony, Kokiri's Emerald, or Song of Time.	You will have Zora's Sapphire, Goron's Ruby, Kokiri's Emerald, Song of Storms, and Song of Time, but not Gold Skulltula Count, Gerudo's Card, or Stone of Agony.
Poacher's Saw	Have Zelda's Lullaby, Prelude of Light, and Requiem of Spirit, but not Sun's Song, Saria's Song, Epona's Song, Nocturne of Shadow, or Serenade of Water.	You will have Zelda's Lullaby, Prelude of Light, Nocturne of Shadow, Requiem of Spirit, and Serenade of Water, but not Sun's Song, Saria's Song, or Epona's Song.
Goron's Sword (Broken)	Have Shadow Medallion, Spirit Medallion, and Fire Medallion, but not Bolero of Fire, Minuet of Forest, Light Medallion, Water Medallion, or Forest Medallion,	You will have Shadow Medallion, Spirit Medallion, Water Medallion, Fire Medallion, and Forest Medallion, but not Bolero of Fire, Minuet of Forest, Light Medallion.

Dungeon Items

Half-milk RBA with Dungeon items is interesting in that you use the "unused" bits. First obtain a value of 24 by RBA'ing the item with a Fairy on B. Then obtain the Compass in the corresponding dungeon to have a value of 26. Finally, empty your B bottle to obtain a value of 31, giving you the Dungeon Map, Compass, and Big Key.

There is a table of the items here: Dungeon Item RBA