Coffee
A hot beverage and served at the Anna Miller's where Kimiko works. Waitresses carry a coffee pot to give free refills to customers. Piro is hit by a coffee pot in Chapter 0 (accidently launched by Kimiko) and later has coffee in poured over his arm in a confused moment (again by Kimiko).
Coffee makes an early appearance in MegaTokyo, first shown in Strip 3. This strip implies Piro and Largo are coffee drinkers, but Dom, not so much. Largo is never again shown to take coffee, ignoring his cup when given one by Erika, as b33r is Largo's beverage of choice.
Erika has been shown to frequently enjoy coffee, especially to start the day (Strips 317, 530, 746, 879), but again it isn't an exclusive drink since she has been shown to enjoy beer (282) and wine (965).
Characters can be shown holding a coffee cup, possibly to give their hands something to do. It should also be remembered that in Japan, vending machines dispense hot coffee in cans, so items such as Erika's drink in Strip 92 is ambiguous.
MegaGear carries a variety of coffee mugs, including a Kimiko's World Famous Lap Pour Blend travel mug.
A hot can of coffee plays a role in the published portion of Warmth.