Combine the brown sugar, water, and apples in a small saucepan. Bring to a boil, then simmer for about 20 minutes, stirring occasionally.
When the apples have softened, pour the mixture into a strainer set over a bowl. Using a spoon, crush the apples to remove as much of the juice as possible. Once you've removed what you can from the apples, pour the syrup into a jar and allow to cool to room temperature. If you're using premade apple syrup, skip the first two steps.
Mix the cinnamon, ginger, cardamom, and cloves in a small bowl. If you have a spice grinder, combine the spices for an even finer consistency.
Combine the boiling water, tea bags, and spice mixture, and allow it to steep for 10 minutes.
Once 10 minutes have elapsed, remove the tea bags and stir the mixture. If you didn't finely grind the spices in the beginning, you may want to strain it through cheesecloth to remove the larger spice particles. Do this by placing a strainer lined with cheesecloth over a bowl. Pour the chai concentrate through the strainer. If you like frosty drinks, let the chai concentrate chill in the fridge for at least 30 minutes before assembling the drink.
Fill your favorite glass with ice and pour the homemade chai concentrate to fill the glass halfway. Add approximately 1/4 cup oatmilk and 1-3 teaspoons sweetener of your choice. Stir to combine.
Combine 1-2 teaspoons of the apple syrup and 1/2 cup oatmilk in a bowl or automatic milk frother. Froth and pour into the glass.
Sprinkle with a dash of cinnamon, and enjoy!