A big irony of course is that disposable cups were once good for your health. Since they are only used once, they're fairly sanitary, and were the great pandemic startup idea of 1918.
https://www.fastcompany.com/90520298/how-dixie-cups-became-t...
https://www.fastcompany.com/90520298/how-dixie-cups-became-t...
If you can avoid both at the same time, terrific! If you can only avoid one, avoid the germs. They will kill you faster.
(Ideally, you also work at reducing/limiting how much exposure you have to the thing poisoning you. Edit: One possible solution here is to drink your coffee cold, such as frappuccino drinks. Even in the same cup, it should be far less of an issue.)
If it's one of the recently trendy 'bamboo' cups, I'm fairly certain most of them are made of predominately with melamine.
https://www.chemistryworld.com/news/reusable-bamboo-mugs-lea...
> Overall, the BfR tested 228 bamboo mugs for formaldehyde and 180 for melamine. In each case, more than 35% of the cups released harmful substances in amounts that surpassed safety limits. Moreover, the amount of melamine – but not formaldehyde – the mugs released increased with repeated exposure to hot and slightly acidic liquids.
https://bluebottlecoffee.com/store/blue-bottle-x-ecoffee-cup