Here’s how to clean a bong with common household products
Step 1: Gather the necessary supplies:
- Isopropyl alcohol, or more commonly known as “rubbing” alcohol
- Sea Salt
- Paper Towels
- Q-Tips
Step 2: Pour equal amounts of salt and alcohol directly into your bowl and/or bong, and shake repeatedly to loosen the black resin from the glass or ceramic. To loosen the harder sticking resin, you can cover the openings of the bowl and/or bong, and flip it upside down and back, multiples times, until the resin has completely loosened from the glass or ceramic. If the alcohol/salt combination appears to be dirty, dump out the solution and repeat from Step 1 until the desired effect is achieved. For the stubborn spots of resin, soak the bowl and/or bong in the solution for a few minutes, and use the Q-Tips to swab away the resin. 
Step 3: Once all of the resin has released, rinse your bowl and/or bong thoroughly with hot water. Congratulations, you’re ready to smoke.