I usually drink coffee, beer, wine, or a liquor while smoking. For new tobaccos, I just pack it and smoke away. The tobacco will usually introduce the flavors and aromas before you realize it.
Distilled water and soda crackers if I am sampling a variety of blends - also a shot of saline spray in the sniffer between bowls to clear the sinuses.
If I am smoking my regular blends, whatever drink my notes suggest to pair with them.
Coffee, wine, spring water - while smoking. For a major palate cleansing - I swish a little peroxide and equal part water in my mouth which seems to do the trick.