I tried dimenhydrinate with salt water about 30 mins ago. 2 tabs right before downing the drink (should have given it some time though). So far, I've been able to hold it, with little nausea at the start which got calmed down in 5 mins. So, with proper protocol it should be feasible.
Both dimenhydrinate and salt burn the throat quite a bit, so I drank a few grams of fresh water.
With SN I should already have been unconscious and CTB in about 20 mins from now - and there is no nausea, only that nasty "butterfly" feeling in the stomach. So, I believe I'm prepared for the real action.
Looks like the trick is to use room temperature water.