Honestly, i did this with muesli and apple juice for years. Only thing that stopped me was finding out how awesome and cheap i can make my own oat milk at home with and the ridiculous sugar apple juice added.
OJ is kinda tangy though, that wouldn't work... Apple was far mellower
This is what we started with, but oats are so cheap increasing the amoint to add to the creaminess is somewhat inevitable:
3 cups water
1/2 cup rolled oats
2 tsp maple syrup
1/2 tsp vanilla extract
1/8 tsp salt
Blend all ingredients together and pour through mesh strainer into a jar with a tight-fitting lid. Don't push the mushy oats through the strainer or else it will be gritty (but its basically porridge)