Was thinking the same - especially as OP said they have trouble drinking in L3.
Nothing wrong with dropping power for a few seconds to enable a drink, it ain't gunna have much impact on the overall L4 workout. e.g. in a 20 minute interval, 10 seconds taken for a drink which, say, sees you drop from 300 watts to 250 watts while getting that drink, will drop your overall 20 minute average less than 1/2 watt.
Better than not staying hydrated.
I had that problem today on a really warm muggy morning. Despite 4 x bidons and a drink stop I still lost 3kg on today's ride
. I needed Floyd's support car!