General:
* Ensoleillé(e) (masculine/feminine) - This is the most common and direct translation of "sunny".
Describing weather:
* Ensoleillé(e) (masculine/feminine) - This is still the most common choice.
* Lumineux(se) (masculine/feminine) - Meaning "bright", this can be used to describe a sunny day.
* Chaud(e) (masculine/feminine) - Meaning "warm", this can also be used to describe a sunny day, especially if it's hot.
Figurative:
* Heureux(se) (masculine/feminine) - Meaning "happy", this can be used figuratively to describe a sunny disposition.
* Optimiste - Meaning "optimistic", this can be used to describe someone who is generally cheerful and positive.
The best translation will depend on the specific context of your sentence.