In a small saucepan, combine 1/2 cup Japanese sake or white wine and 1/3 cup brown sugar and bring to a boil on low-medium heat. Boil for one minute to boil off alcohol content and enhance the rich flavor of the sake.
Bring temperature down to low and add 1 clove minced garlic, 1 tsp minced ginger, 2 tbsp honey, and 1/4 cup fruit puree or 100% fruit juice of your choice to the saucepan. Stir to combine.
Add 1/2 cup dark soy sauce (such as Kikkoman) and continue to stir the mixture.
Add 2 tbsp roasted sesame oil, 2 tbsp white roasted sesame seeds, 1 tsp chopped green onion, and 1 dried red hot chili pepper (optional) to the saucepan. Stir to combine.
Let the sauce sit on low heat for 10 minutes, stirring frequently.
Remove the sauce from the heat and let it cool to room temperature before using. If desired, strain the sauce through a fine-mesh sieve to remove any solids.
Serve the Japanese BBQ sauce with your favorite grilled meats, vegetables, or seafood.