Caffeine per se won't wreck your palate, but strong flavors like in coffee can make you less sensitive to subtle flavors.
Generally, ANY strong flavored foods/drinks that overwhelm your taste buds should be avoided before judging. Hot peppers, rich/spicy foods like Indian or Thai can dull the senses.
One of the best palate cleansers I ever had was back about 6 or 7 years ago at 1st Round NHC judging. We were judging the Light Hybrids flight and someone entered a cream ale that had developed a very pronounced (but very clean) lactic acid contamination. Despite its low score as a Cream Ale, we kept it on the table for the rest of the round as a delicious palate cleanser. (We called it the Berliner Cream Ale.)
Plain crackers or plain white/French bread, and a bit of water seem to do the trick for me.
The idea is to mellow it all out and give your taste buds a break.