While hard seltzer is low in calories and carbs, most dietitians wouldn't call it healthy. It's easy to drink, and it doesn't make you feel full like beer can. So it's easy to have too many. The calories can add up. So, too, can the alcohol, which might lead to bad judgment in the short term and affect your health if you make it a habit. Enjoy them in moderation. Stick to one a day if you're a woman, or two if you're a man.