How to select an entity with a named item in their offhand in Minecraft 1.14?
Solution 1:
You have different names for the stick. One is escaped and one is not. Without escaping the name it can't be interpreted properly, since it is inside another tag which already interprets the quotes.
Escape the name properly in your /effect command and it will work (tested and works for me):
/effect give @a[nbt={Inventory:[{Slot:-106b,id:"minecraft:stick", tag:{display:{Name:"\"Speed Stick Deodorant\""}}}]}] minecraft:speed 1 7 true