Sanji personally doesn’t want to eat a Devil Fruit because he doesn’t want to become unable to swim.
The reason behind it is, well obviously he is extremely strong even without eating a Devil Fruit and his speed and foot work make him a formidable opponent even when he is underwater and lastly the most important reason being the “All Blue”. Of course to see the All Blue when he finds it he needs to go underwater and being a devil fruit eater makes it difficult.
Now with all the reasons to not eat a devil fruit there are a few special Devil Fruit abilities which will over turn all the above reasons when it comes to Sanji. I can think of three, let’s see what they are:
1. Suke Suke no Mi
The Suke Suke no Mi is a Paramecia-type Devil Fruit that gives its user the ability to turn himself and anything he touches invisible, making the user an Invisible Human.The invisibility effect can extend to objects like portable hand-strapped cannons and small ships used for evacuation. It was initially eaten by Absalom, and after his death, it was eaten by Shiliew of the Rain.
Well it was shown in the anime, during Thriller Bark arc, that it was Sanji’s dream to eat this Devil Fruit in spite of the side effects so he could help people(Peek at Women’s bath), do good for humanity(Peek at Women’s bath) and when he gets time(Peek at Women’s bath) but his dream was shattered because Absalom had already eaten that Devil Fruit.
2. Giro Giro no Mi
The Giro Giro no Mi is a Paramecia-type Devil Fruit that allows the user to see through everything and read the minds of others, allowing the user to become an Insight Human. It was eaten by Viola.
Giro Giro no Mi also allows you to see as far as 4000 kms which means you can virtually look anywhere you want even the places which just popped into your mind. When Viola told Luffy about her abilities he commented,”now that’s an ability Sanji would want”.
3. Mane Mane no Mi
The Mane Mane no Mi is a Paramecia-type Devil Fruit that allows the user to turn into a physical double of anyone he or she has touched, making the user an Imitating Human. When the user changes, they also imitate the copied person’s flexibility, strength, and abilities, aside from those bestowed by a Devil Fruit. They can change to someone else by touching their face with their right hand and switch back to their normal state by touching their face with their left hand. It was eaten by Bentham, better known by his Baroque Works alias Mr. 2 Bon Kurei.
As the Ability allows its user to turn into anyone they want you can guess how happy Sanji would be if he could get his hands on this ability. We all remember Punk Hazard when he, for a few episodes, switched his body with Nami. With this ability he can do this anytime and with anyone! 😀