How i add in this script, the function to equip the tool too?

I agree with what the above person said; UserInputService is the better, easier, and more developed method.

User Input Service

User input service is fairly easy to use and is actually better than the other service you're currently using. It's also a lot more versatile as you can use `InputBegan`; `InputChanged`; `InputEnded`, `JumpRequest()`; `GamepadConnected`; etc etc etc. Basically, if you're ever planning on making your game multi-platform, you should consider using `UserInputService`. By what you're trying to do, I would suggest `InputBegan`. 

Here's an example script

local userInputService = game:GetService("UserInputService")

userInputService.InputBegan:connect(function(key)
    if key.KeyCode == Enum.KeyCode.E then
        print("The letter E was pushed")
    end
end)

Here is this implemented into your script:

local plr = game.Players.LocalPlayer
repeat wait() until plr.Character
local plrc = plr.Character
local toolName = script.Parent.Name
local replicatedStorage = game:GetService("ReplicatedStorage")
local fruit = replicatedstorage:WaitForChild("Skills"):WaitForChild(script.Parent.Parent.Parent.Parent.Stats.AkumaNoMi.Value)
local tool = fruit:WaitForChild(script.Parent.Name)
local uis = game:GetService("UserInputService")

uis.InputBegan:connect(function(key)
    if key.KeyCode == Enum.KeyCode.E and script.Parent.Reloading.Value == "No" then
        local toolCloning = tool:Clone()
        toolCloning.Parent = plr.Backpack
        wait(0.25)
        plrc.Humanoid:EquipTool(toolCloning) 
    end
end)

Another thing: I noticed that you used script.Parent.Parent.Parent.Parent.Backpack.toolname which isn't the proper method. If you're looking for an item via it's name and it's not in string format, then use script.Parent.Parent.Parent.Parent.Backpack[toolname] as this will look for the tool with toolname instead of literally toolname.

If this helped, then please accept my answer!

You are using the Mouse.KeyDown event, which is deprecated and most likely will not work. UserInputService and ContextActionService is more preferred over.

So there are two method to do this.

UserInputService method:

wait()
local toolname = script.Parent.Name
local replicatedstorage = game:GetService("ReplicatedStorage")
local fruit = replicatedstorage.Skills:WaitForChild(script.Parent.Parent.Parent.Parent.Stats.AkumaNoMi.Value)
local tool = fruit:WaitForChild(script.Parent.Name)
local plr = game.Players.LocalPlayer
local plrc = plr.Character
local UIS = game:GetService("UserInputService")



function PressE(input, gpe) 
    if input.KeyCode == Enum.KeyCode.E then
        if script.Parent.Reloading.Value == "No" then
        local toolCloning = tool:Clone()
        toolCloning.Parent = plr.Backpack
        wait(0.25)
        plrc.Humanoid:EquipTool(script.Parent.Parent.Parent.Parent.Backpack.toolname)
    end
  end
end
UIS.InputBegan:Connect(PressE)

ContextActionService method:

wait()
local toolname = script.Parent.Name
local replicatedstorage = game:GetService("ReplicatedStorage")
local fruit = replicatedstorage.Skills:WaitForChild(script.Parent.Parent.Parent.Parent.Stats.AkumaNoMi.Value)
local tool = fruit:WaitForChild(script.Parent.Name)
local plr = game.Players.LocalPlayer
local plrc = plr.Character



function PressE(actionName, userInputState, inputObject) 
    if userInputState == Enum.UserInputState.Begin then
        if script.Parent.Reloading.Value == "No" then
        local toolCloning = tool:Clone()
        toolCloning.Parent = plr.Backpack
        wait(0.25)
        plrc.Humanoid:EquipTool(script.Parent.Parent.Parent.Parent.Backpack.toolname)
    end
  end
end
game.ContextActionService:BindAction("keyPress", PressE, false, Enum.KeyCode.E)

Either way can be used and they will work as expected.

If it still doesn’t work: check if the Reloading value is set to "No" and your tool is named "toolname" (because the script refers it)

Hope this helps.