Handheld games:

Generation III:

A Sitrus Berry, if held by a Pokémon, can restore 30 HP when its HP drops to below ⅓, or can be used as an item to restore 30 HP at any time.

 

Generation IV:

When held by a Pokémon, a Sitrus Berry will restore ¼ of its HP when its HP drops to below ½. It can also be used as an item to restore ¼ of a Pokémon's HP at any time.

 

Generation V

When held by a Pokémon, a Sitrus Berry will restore ¼ of its HP when its HP is below ½. It can also be used as an item to restore ¼ of a Pokémon's HP at any time. . .

PRO:

A Sitrus Berry, if held by a Pokémon, can restore 25% of max/HP when its HP drops to below ⅓.

 

It can also be used as an item to restore 30 HP of a Pokémon at any time.

-snip-

^visual

 

my first response to this >

 

GEN III:

A Sitrus Berry, if held by a Pokémon, can restore 30 HP when its HP drops to below ⅓, or can be used as an item to restore 30 HP at any time.

GEN IV:

When held by a Pokémon, a Sitrus Berry will restore ¼ of its HP when its HP drops to below ½. It can also be used as an item to restore ¼ of a Pokémon's HP at any time.

GEN V:

When held by a Pokémon, a Sitrus Berry will restore ¼ of its HP when its HP is below ½. It can also be used as an item to restore ¼ of a Pokémon's HP at any time.

 

Visual:

 

The berry is either stuck in Gen3 when used on a pokemon but afaik it works when someone is holding it as an item.