Trader Joe's will offer up single-serve snacks and treats for customers to nibble on, but hot coffee won't return, according to employees at New York and California stores.The samples make everything a little bit better," said Natasha Fischer, who runs @traderjoeslist, an Instagram account and newsletter documenting the latest Trader Joe's finds.Companies want you to have a bite at the store to get your saliva glands working as you browse around, said Paco Underhill, the founder of behavioral research and consulting firm Envirosell and author of "How We Eat: The Brave New World of Food and Drink.Startup food brands rely on store demos to introduce customers to their products and get their feedback, said Yuval Selik, the CEO of Promomash, a company that works with brands on samples and promotion strategy."Demos have long been one of our members' favorite experiences when they visit our clubs," a Sam's Club spokesperson said."