Coffee

A single serving method (from James Hoffman YT channel) I use is:

16g coffee 150g water 100g ice

I make the hot coffee using the above 16g coffee and 150g water. My brew time is four minutes. Then, I pour that hot coffee over the ice and stir until the ice cubes are melted.

Have you tried freezing extra/left over coffee in an ice tray and using those to chill your coffee?

Whiskey stones. Get solid stones or stainless steel ones. Ideally don't get any with liquid cores.

You might try the Toddy cold brew method. You take like a pound of beans, grind them up and soak in like a gallon of water that slow filters through a special filter they sell (reusable for 10 uses). Then you keep it in the fridge until you use it. It’s a more mellow, less acidic brew in general.

Cold brew shaken with lots of ice (and if you are me, some simple syrup). Cold brew is strong and smooth, and using more ice in shaker lowers the temp fast so less dilution. Strain over more ice in insulated cup.