Plain digestives in tea. I grab about five of them all sandwiched together, dunk in a wide rimmed mug up to half way then take a big bite of the soft bit. Yum! Like eating an adult version of baby farley’s rusks! Can you tell I get through a packet of Digestives pretty quickly?
Bourbons are by far the most superior dunking biscuit for a quick filling snack, but they can’t be cheap ‘white label’, they must be of decent quality.
Shortcake fingers are another good dunker, but these require a good few seconds to soak.
Hob nobs are too bitty and can make a mess of the brew.
Rich Tea are useless, you need to eat about 30 biscuits to make it worth your while and by that time you’ve no brew left.