Kinetic energy bar
A kinetic energy bar is a type of healing artifact. When consumed, the hero will regain a limited amount of hit points. The trade-off is the high price paid for this low heal. However; since this is a growing trend, some shop keepers charge more than others in the hopes that a hero will be so interested in looking cool they will literally pay for this privilege. Some flavors taste better than others with personal preferences also being a factor - however, the best selling flavor is habanero-covered chocolate bar with jalapeño pepper.
However; sometimes heroes will be fooled into purchasing a normal granola bar instead, in which case the hero will gain nothing (and write angrily in their diary about it) and lose a good number of coins.