Your add-on is missing a code piece to execute itself, for one.
Two, your namecheck is different from the add-on name, so it won't execute.
Three, once those two bugs were fixed I found these:
Loading Add-On: Item_CritACola (CRC:2134848481)
Executing Add-Ons/Item_CritACola/server.cs.
Executing Add-Ons/Item_CritACola/Item_CritACola.cs.
Could not locate shape: Add-Ons/Item_CritACola/critacola.dts (download failed)
Add-Ons/Item_CritACola/Item_CritACola.cs (72): preload failed for fpRedsodaImage: Unable to load shape: Add-Ons/Item_CritACola/fpRedsoda.dts.
Activating package: fpRedsodaPackage
5 datablocks added.
Could not locate texture: Add-Ons/Item_CritACola/drink (download failed, using default texture)
+- using blank texture
Could not locate shape: Add-Ons/Item_CritACola/critacola.dts (download failed)
critcola.dts (located in the .zip) should be renamed to critacola.dts. Simple typo mistake.
As for the texture "drink" and the texture "Crit___a___Cola_Bonk_by_borzo
u99j", they do not exist in the .zip so I can't help here.
I managed to get it in-game. Your code has some bugs, as the player won't hold it when obtained. Your model is oversized as well.
Oh another question why do all my weapons turn out side ways?
You must have it sideways in the modeling program.
Rotate it.