Teresa Simmermacher buys a container of Starbucks Via, Tuesday, in New York. Caffeine addicts across North America got first tastes of Starbucks Corp.’s newest offering as the coffee giant blanketed the nation with tens of thousands of free samples of Via. The beverage, which comes in a long cylindrical plastic sleeve and dissolves in a cup of water, debuted nationwide Tuesday after months of preliminary sales in test markets. The windows of Starbucks stores across Canada were plastered with signs announcing the arrival of Via as part of the chain’s quest to convince customers that instant coffee — long viewed as inferior by U.S. coffee drinkers — can taste as good as brewed. Verdicts from an unscientific sampling of customers ranged from a tentative thumbs-up to serious skepticism.