How do you create a global property like a $ property that can be accessible everywhere?

I don’t need/want to use vuex store for this as I’m not writing data. It is only to read data globally.
Sort of like how you can access this.$vuetify.theme everywhere, how can I register athis.$myproperty in my app so that I can just reference it everywhere?
Attaching it to Vue.prototype.$myproperty does not work.