To make the barbecue soy sauce thick and able to hang on the food, you can try the following methods:

1. Add thickeners: Using some thickeners can Helps the BBQ sauce become thicker. Commonly used thickeners include starch, corn flour, corn flour, etc. Mix an appropriate amount of thickener with a small amount of water to form a paste, then add it to the barbecue soy sauce and stir evenly to make it thick.

2. Cook the sauce to thicken it: You can thicken the barbecue soy sauce to evaporate the water and condense it into a thick state. Pour the soy sauce into the pot, bring to a slow boil over medium-low heat, then reduce to low and continue cooking until the soy sauce thickens.

3. Add other seasonings: You can add some other seasonings according to your own taste, such as honey, brown sugar, peanut butter, etc. These seasonings can increase the viscosity of the barbecue soy sauce.

Remember, make appropriate adjustments when performing the above operations to avoid adding too many thickeners or seasonings, which may cause the soy sauce to become too thick or too strong in flavor.

If the above methods still cannot achieve the required viscosity, it may be due to improper ingredients or proportions, or the characteristics of the soy sauce itself. At this point, you can make adjustments by referring to recipes or product recommendations from other chefs, or try other brands of barbecue soy sauce.