If you don't feel like cooking and/or catching your meals, you're in luck. Abisko Turiststation has a restaurant open for all three meals. Breakfast costs SEK 90, Lunch (either at the restaurant or packed) costs SEK 80, and Dinner costs SEK 270 (or Kr 290 with no reservation). Obviously, to save maximum money, it makes sense to have a picnic dinner. Water, juice, and coffee are included.
Breakfast and Lunch are buffet affairs, while Dinner is a set meal. Inquire at the front desk to ensure the meal doesn't conflict with any dietary restrictions you have.
If you're staying at the Turiststation, you can get half-pension or full-pension included if you wish. Half-pension will save you Kr 20-40 over Breakfast and Dinner purchased separately. If you book full-pension, you will save Kr 30-60 off the pay-as-you-go price (assuming you eat all of the meals you pre-paid for).
Favorite Dish: OK, so why do I rate this so highly? We were here over Midsummer, and had the good fortune to participate in a traditional Midsummer dinner buffet. The food was magnificent. See my "local customs" tip on this page for more details.
There is nice restaurant at the hostel serving some nice local food, and not only Swedish meatballs, so you might want to try it
If you going on a long day trip pack your stuff and be prepared for long day without any opting to eat anything but what you carry on with you. So, a picnic in the forest is always a good option