Chewing 6 or 8 blanched almonds during an episode of heartburn may relieve the symptoms. Chew them well, though, to avoid swallowing air and causing yourself more discomfort.
You can also try brown rice, plain or with a little sweetening. Rice is a complex carbohydrate and is a bland food, which is less likely to increase acidity or relax the sphincter muscle.
Soda crackers (preferably unsalted) are bland, they digest easily, and they absorb stomach acid as well. They also contain bicarbonate of soda and cream of tartar, which neutralize the acid. Tip: You know that package of soda crackers they always give you at the restaurant, that you leave on the table? From now on, take them with you. These come in handy when you're plagued by heartburn and can't seek immediate relief.