From Pikipedia, the Pikmin wiki
The Sunseed Berry (ヒダマリノミ?, lit.: "Sunny Spot Seed") is a treasure found in Pikmin 2 and a fruit in Pikmin 3. It is actually a regular strawberry. In Pikmin 2, it is found on the Awakening Wood, while in Pikmin 3, there are four of them: three in the Garden of Hope and one in the Distant Tundra.
Collecting the treasure
The Sunseed Berry is found sitting on a ledge just across from the landing site in Awakening Wood, and can easily be obtained, as it is guarded only by a Red Bulborb and two Dwarf Red Bulborbs. The ledge is low enough that any type of Pikmin can be thrown up to collect the treasure. Alternately, you can go around to the path that leads to the Snagret Hole and get it there, but this is more time consuming and dangerous.
Collecting the fruit
Garden of Hope (Brittany's crash site)
Garden of Hope (riverside)
Another Sunseed Berry is on a ledge by a pile of Fragments used to build an orange bridge; defeat the Skutterchucks nearby, as they may throw crystals at the player's Pikmin.
Garden of Hope (underwater)
The last Sunseed Berry in the area is underwater, past the large cinderblock after Louie runs away. It is near a dirt wall. It is protected by several Puckering Blinnows, which should be defeated so the Pikmin can safely get the fruit.
In the Distant Tundra, the only Sunseed Berry is inside a Pyroclasmic Slooch, which is in an enclosed area sealed off by a crystal wall, along with another Slooch. Along the way back there is a Joustmite and a Bearded Amprat; defeat these as well to ensure the Pikmin have a safe route back to the ship.
“I found this fascinating fruit while out exploring today. The skies cleared up, and I felt peaceful watching the pink flower petals flutter in the wind. During this perilous expedition, it seems strange to have such softhearted, romantic thoughts. If I told my wife about this, I'm sure I'd get laughed at...again.”
“This fruit is born of bright sunlight and cheerful warmth. Come, all you gloomy naysayers! One bite and even sad sacks will become foolhardy optimists. Eat one today and change your life!”
“As a scientist and as a food eater, I'm excited about this new source of potential nutrition. I just wish it didn't look like it was covered in pimples. Luckily, the taste of it is like delicious and scrumptious had a baby. Let's gather as many of these as we can!”
“I've never experienced anything like it. Scientifically speaking, the flavour straddles the boundary between scrumptious and delicious, and can only be described as 'scrumplicious'. On the down side, this fruit appears to have a nasty case of pimples.”
Golden Sunseeds are fruits found in Pikmin 3's Mission Mode and Bingo Battle. They are a golden variety of Sunseed Berries, and are thus very valuable: they are worth × 200. Aside from being worth four times as much as Sunseed Berries, they are functionally identical to their regular counterparts.
Names in other languages