A Link to the Past Bottles

The first bottle can be purchased from the merchant in Kakariko Village for 100 Rupees.

The second bottle can be obtained by going into the Kakariko Tavern (the long building in Kakariko Village) through the back entrance. To enter the back way, simply walk through the building from the space in the hedges in the back wall of the building. Inside will be a treasure chest containing the second bottle.

To get the third bottle, you must first acquire the Zora's Flippers. It is located underneath the bridge east of your house. Simply jump into the water at the closest area to the bridge, and swim around until you get under it. You will find someone under there camping. Talk to him, and he will give you the third bottle.

To get the fourth and final bottle, you must have completed the fourth Dark World Dungeon and obtained the Tempered Sword and the Titan's Mitts. In the Dark World, go to where the blacksmith's hut would be in the Light World, and there will be a destroyed shack there instead. Inside, you will find a treasure chest housing the last bottle, but you cannot open it yet. Instead, it will follow you around. Take it to the man sitting next to the sign by the entrance to the desert in the Light World, and he will open the chest for you.