Years ago I once gunged myself with melted ice cream. I used a 2L tub, and from memory I seem to remember that I thought I got a bit burnt (similar to light sunburn).

So my questions are what's the best sized tub to use and what's the best type of flavour to use? Back then I used lime flavoured ice cream.

Avoid lime juice, it commonly causes skin reactions.

Most other flavours will be fine.

I once did this. Ice cream plus syrup. In retrospect, I should have skipped the syrup because it washed most of the ice cream away, but it was really fun overall.

https://umd.net/forums/how-long-to-melt-48oz-ice-cream

Would recommend those flavors! Or any flavors you enjoy. Personally I'd avoid ice cream with chunky things in them for drain safety.