Wash item by hand. You can utilize a pipe cleaner for the inside of the straw and down stem to remove any residue that may build up, also isopropyl alcohol and salt can be a good solvent for cleaning inside of the tumbler. You can also purchase several different cleaners for water pipes at your local Head Shop or even on Amazon!
We recommend this one from Amazon, it's great! You can get it by going here*: https://amzn.to/48CwhVA
*Do not drink out of tumbler after having used it for smoking*
*Above is an affiliate link that will give me a small commission for sharing it, it costs you nothing of course for purchasing from my link!)