Dented can of iced tea fizzed when opened

It fizzed a bit when opened, like soda sort of and sprayed on my hand, after that it was flat.

I see this happen all the time with cans of uncarbonated drinks, e.g. Arizona iced tea. Even though the drink isn't carbonated, the cans seem to be pressurized to some degree: an unopened can is quite firm and hard to squeeze, while cans that have been opened even just a tiny bit yield easily. Also, you can hear the hiss of escaping gas as you open the can.

I've also seen these cans spray somewhat when they're opened, mostly after they've been shaken. My guess here is that shaking the can mixes the gas and liquid, and when you open the can the bubbles of gas in the liquid expand quickly as the pressure drops. I've never seen a can of tea spray nearly as much as a vigorously shaken can of soda would, but it enough to wet your hand a bit or spread a few drops on nearby surfaces.

This is not a botulism risk is it?

I doubt it -- botulism does not like acidic environments, and one source I found puts the pH of Lemon Brisk at 2.86, which is pretty acidic.

I put it down the drain but not sure how much cleaning up I need to do.

I'd wipe the area with a damp towel to remove the sugar, which will make things sticky as it dries. Other than that, I think you're pretty safe.